Treated brine compositions with reduced concentrations of potassium, rubidium, and cesium

ABSTRACT

This invention relates to treated geothermal brine compositions containing reduced concentrations of silica, iron, and potassium compared to the untreated brines. Exemplary compositions of the treated brine contain a concentration of silica ranging from about 0 mg/kg to about 15 mg/kg, a concentration of iron ranging from about 0 mg/kg to about 10 mg/kg, and a concentration of potassium ranging from about 300 mg/kg to about 8500 mg/kg. Other exemplary compositions of the treated brines also contain reduced concentrations of elements like rubidium, cesium, and lithium.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/780,308, filed on Mar. 13, 2013, and U.S. Provisional PatentApplication Ser. No. 61/873,212, filed on Sep. 3, 2013; also claimspriority to, and is a Continuation-in-Part of U.S. patent applicationSer. No. 14/062,781, filed on Oct. 24, 2013, which is a Continuationapplication of U.S. Pat. No. 8,597,521 filed on Jun. 24, 2010, whichclaims priority to U.S. Provisional Patent Application Ser. No.61/220,000, filed on Jun. 24, 2009; also claims priority to and is aContinuation-in-Part of U.S. patent application Ser. No. 12/823,000,filed on Jun. 24, 2010, which claims priority to U.S. Provisional PatentApplication Ser. No. 61/239,275, filed on Sep. 2, 2009, all of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD OF THE INVENTION

The invention generally relates to treated brine compositions withreduced concentrations of silica, iron, and potassium. Certainembodiments of the invention also relate to the geothermal brinecompositions with reduced concentrations of silica and iron from whichpotassium, rubidium, and/or cesium, selectively or in combination, havebeen removed. Additionally, the invention relates to methods ofproducing these treated brine compositions using tetrafluoroborates.

BACKGROUND

A number of brine sources exist naturally. For instance, brine sourcesinclude brine deposits like the Salar de Atacama in Chile, Silver PeakNev., Salar de Uyuni in Bolivia, or the Salar de Hombre Muerte inArgentina. Other common brine sources are geothermal, oilfield,Smackover, and relict hydrothermal brines. These brines, however, havenot previously been commercially exploited very well.

Geothermal brines are of particular interest for a variety of reasons.First, geothermal brines provide a source of power due to the fact thathot geothermal pools are stored at high pressure underground, which whenreleased to atmospheric pressure, can provide a flash-steam. Theflash-steam can be used, for example, to run a power plant.Additionally, geothermal brines contain useful elements, which can berecovered and utilized for secondary processes. In some geothermalwaters and brines, binary processes can be used to heat a second fluidto provide steam for the generation of electricity without the flashingof the geothermal brine.

One problem associated with geothermal brines when utilized for theproduction of electricity results from scaling and deposition of solids.Silica and other solids that are dissolved within the geothermal brineprecipitate out during all stages of brine processing, particularlyduring the cooling of a geothermal brine, and may eventually result infouling of the injection wells or processing equipment.

It is known that geothermal brines can include various metal ions,particularly alkali and alkaline earth metals, as well as silica, iron,lead, silver, and zinc, in varying concentrations, depending upon thesource of the brine. Recovery of these metals is potentially importantto the chemical, pharmaceutical, and electronic industries. Typically,the economical recovery of metals from natural brines, which may varywidely in composition, depends not only on the specific concentration ofthe desired metal, but also upon the concentrations of interfering ions,particularly silica, calcium, and magnesium, because the presence of theinterfering ions will increase recovery costs, as additional steps mustbe taken to remove the interfering ions. Economical recovery alsodepends upon the commercial cost and availability of the desired metalalready present in the relevant market.

Some of the desired metals that can be present in brines are potassium,rubidium, and cesium. Economically recoverable deposits of potassium arerare. The potassium concentration in the Salton Sea geothermal brine,however, is around 24,000 parts per million. Potassium that has beenextracted from brines can easily be converted into potassium chloride,which is useful in a variety of applications including agriculture,medicine, food processing, and as a standard measure of conductivity ofionic solutions in the chemical arts.

Currently, there are no existing potassium, rubidium, and cesium removaltechnologies that remove potassium, rubidium, and/or cesium, selectivelyor in combination, from geothermal brines generally. Therefore, it wouldbe advantageous to develop a method to remove potassium, rubidium,and/or cesium, selectively or in combination, from brines and convertthem into chlorides. Additionally, this technology presents an economicadvantage. For example, the price of potassium chloride in the chemicalmarket is relatively low, so it would be advantageous to develop amethod of production of potassium chloride using extracted potassiumfrom geothermal and other brines that is cost competitive.

Silica is known to deposit in piping as scale deposits, typically as aresult of the cooling of a geothermal brine. Frequently, geothermalbrines are near saturation with respect to the silica concentration andupon cooling; deposition occurs because of the lower solubilities atlower temperatures. This is combined with the polymerization of silicaand co-precipitation with other species, particularly metals. This isseen in geothermal power stations, and is particularly true foramorphous silica/silicates. Additionally, silica is a known problem inreverse osmosis desalination plants. Thus, removal of silica from lowconcentration brines may help to eliminate these scale deposits, andthus reduce costs and improve efficiency of facilities that use andprocess brines.

Known methods for the removal of silica from geothermal brines includethe use of a geothermal brine clarifier for the removal and recovery ofsilica solids that may be precipitated with the use of various seedmaterials, or the use of compounds that absorb silica, such as magnesiumoxide, magnesium hydroxide, or magnesium carbonate. In addition to aless than complete recovery of silicon from brines, prior methods alsosuffer in that they typically remove ions and compounds other than justsilica and silicon containing compounds.

Geothermal brines can be flashed via several processes. There is theconventional method to produce steam for power. There have also beenmodifications to the conventional dual direct flash evaporation methodto include multiple flash evaporation stages.

One modification to the conventional dual direct flash method is thecrystallizer reactor clarifier process. In the crystallizer reactorclarifier process, a reactor clarifier precipitates components that cancause scaling, such as iron rich amorphous silica, and removes suspendedparticles from the brines before injection into the flash process. Theprocess also seeds the brine in the flash vessels to reduce scaleformation. Thus, when precipitation occurs it is more likely that itwill occur on the seed slurry than on the metal surfaces of the flashapparatus.

There is also the pH modification process that differs from thecrystallizer reactor clarifier process. In the pH modification process,compounds that cause scaling are maintained in solution. By lowering thepH of the brine solution, for example, as low as 3.0, compounds thattypically cause scaling on the flash apparatus are maintained insolution. By lowering pH and modifying pressures, the compounds aremaintained in solution and scaling is prevented or reduced.

Thus, although conventional methods employed in the processing of oresand brines can remove some of the silica present in silica containingsolutions and brines, there exists a need to develop methods that areselective for the removal of silica from brines and other silicacontaining solutions at high yields to produce treated compositions withreduced silica concentrations. Additionally, once certain components areremoved, the geothermal brine compositions may be injected into ageothermal reservoir, such as into the original reservoir. Compositionsfor improving injectivity of such brines will improve the efficiency ofthe process, as improved injectivity will reduce the costs and timeassociated with cleaning the equipment used for injecting such brinesand will also increase long-term permeable flow. While current practicesat geothermal plants have focused on reduction of scaling on theapparatus associated with the flash process, there is still a need toreduce scaling after the processing of the brine for energy. The currentpractice at Salton Sea geothermal plants is to clean injection wells onan annual basis. This is a significant expense as there are typicallymultiple wells (i.e., three wells) to clean out. This is typically doneby hydroblasting or acid treatment. After a certain time, typicallythree years, this is no longer effective and portions of wells must berouted out to remove blockages, which is expensive and time consuming.The routing process can usually be repeated twice before the wells haveto be completely replaced. Thus, compositions and processes that wouldreduce fouling and prolong the time between required cleanings would beof substantial benefit.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention include treatedgeothermal brine compositions. In certain embodiments, the compositioncontains a treated geothermal brine having a concentration of silicaranging from about 0 mg/kg to 15 mg/kg, a concentration of iron rangingfrom about 0 to about 10 mg/kg, and a concentration of potassium rangingfrom about 300 mg/kg to about 8500 mg/kg. The compositions can be usedfor further mineral extraction or for injection into a geothermalreservoir.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 10 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 4000 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 5 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 4000 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 10 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 2000 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 5 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 1000 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 10 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 1000 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 10 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 500 mg/kg.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica less than about 5 mg/kg,the concentration of iron less than about 10 mg/kg, and theconcentration of potassium less than about 500 mg/kg.

In other aspects, the treated geothermal brine compositions describedherein have a concentration of rubidium ranging from about 30 mg/kg toabout 200 mg/kg.

In other aspects, the treated geothermal brine compositions describedherein are Salton Sea geothermal brines. In other aspects, the treatedgeothermal brine compositions described herein are concentratedgeothermal brines. In other aspects, the treated geothermal brinecompositions described herein are used in a mineral extraction process.In other aspects, the treated geothermal brine compositions describedherein are injected into geothermal reservoirs.

In other aspects, the invention provides a treated geothermal brinecomposition having a concentration of silica ranging from about 0 mg/kgto about 15 mg/kg, a concentration of iron ranging from about 0 mg/kg toabout 10 mg/kg, and a concentration of rubidium ranging from about 30mg/kg to about 200 mg/kg. In other aspects, this treated geothermalbrine composition having a concentration of potassium of less than about4000 mg/kg.

Some aspects of the present invention include methods of removing silicaand iron from brines, as well as removing potassium, rubidium, and/orcesium, selectively or in combination from brines usingtetrafluoroborates, as well as compositions that result therefrom. Themethod includes providing a brine solution that includes potassium,rubidium and/or cesium dissolved therein and then contacting the brinesolution with a tetrafluoroborate compound to produce atetrafluoroborate precipitate and an aqueous layer. Thetetrafluoroborate precipitate containing potassium, rubidium and/orcesium is then separated from the aqueous layer.

In other aspects, the invention provides a method for preparingpotassium chloride, rubidium chloride and/or cesium chloride from atetrafluoroborate. The method includes contacting potassiumtetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate with an ionic liquid containing chloride anions toproduce a tetrafluoroborate/ionic liquid solution. Thetetrafluoroborate/ionic liquid solution is then heated to produce atetrafluoroborate layer and an aqueous layer. The tetrafluoroboratelayer is then separated from the aqueous layer and the aqueous layer isevaporated to produce potassium chloride, rubidium chloride, and/orcesium chloride.

In another aspect, the invention provides a method for preparing achloride from a solution containing potassium tetrafluoroborate,rubidium tetrafluoroborate, and/or cesium tetrafluoroborate. The methodincludes contacting potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate with an aqueoussolution containing an ion-exchange media to produce atetrafluoroborate/ion-exchange media mixture. Thetetrafluoroborate/ion-exchange media mixture is then heated to producean ion-exchange media layer and an aqueous layer. The aqueous layer isthen separated from the ion-exchange media layer. The aqueous layer isthen evaporated to produce a potassium, rubidium and/or cesium chloride.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and benefits of the invention,as well as others which will become apparent, may be understood in moredetail, a more particular description of the embodiments of theinvention may be had by reference to the embodiments thereof which areillustrated in the appended drawings, which form a part of thisspecification, it is also to be noted, however, that the drawingsillustrate only various embodiments of the invention and are thereforenot to be considered limiting of the invention's scope as it may includeother effective embodiments as well.

FIG. 1 is an illustration of an apparatus for the removal of silica froma silica containing brine according to an embodiment of the presentinvention.

FIG. 2 is an illustration of an apparatus for the removal of silica froma silica containing brine according to an embodiment of the presentinvention.

FIG. 3 is an illustration of an apparatus for the removal of silica,from a silica containing brine according to an embodiment of the presentinvention.

FIG. 4 is an illustration of an apparatus for the removal of silica froma silica containing brine according to an embodiment of the presentinvention.

FIG. 5 is an illustration of a process for the removal of silica andiron from a geothermal brine, followed by the subsequent removal oflithium according to an embodiment of the present invention.

FIG. 6 is an illustration of a continuous process for the management ofsilica according to an embodiment of the present invention.

FIG. 7 shows a process according to an embodiment using a pHmodification process.

FIG. 8 shows a process according to an embodiment using a crystallizerreactor clarifier process.

FIG. 9 shows a process according to an embodiment using a crystallizerreactor clarifier process.

FIG. 10 is a flow diagram of selectively extracting potassium andrecovering potassium chloride from brines using ionic liquids.

FIG. 11 is a flow diagram of selectively extracting potassium andrecovering potassium chloride from brines using ion exchange media.

FIG. 12 is a graph showing the packed bed differential pressure versustime for an untreated brine.

FIG. 13 is a graph showing the packed bed differential pressure versustime for an untreated brine.

FIG. 14 is a graph showing the packed bed differential pressure versustime for an untreated brine.

FIG. 15 is a graph showing the packed bed differential pressure versustime for a 50:50 blend brine.

FIG. 16 is a graph showing the packed bed differential pressure versustime for a 50:50 blend brine.

FIG. 17 is a graph showing the packed bed differential pressure versustime for a 50:50 blend brine.

FIG. 18 is a graph showing the packed bed differential pressure versustime for a treated brine.

FIG. 19 is a graph showing the packed bed differential pressure versustime for a treated brine.

FIG. 20 is a graph showing the packed bed differential pressure versustime for a treated brine.

FIG. 21 shows the chemistry of an untreated brine before and alterpacked bed testing.

FIG. 22 shows the chemistry of a treated brine before and after packedbed testing.

FIG. 23 shows the chemistry of a treated brine before and after packedbed testing.

FIG. 24 shows the chemistry of a 50:50 blend brine before and afterpacked bed testing.

FIG. 25 shows the chemistry of a 50:50 blend brine before and afterpacked bed testing.

FIG. 26 shows a SEM image from a packed bed test of untreated brine.

FIG. 27 shows a SEM image from a packed bed test of untreated brine.

FIG. 28 shows a SEM image from a packed bed test of treated brine.

FIG. 29 shows a SEM image from a packed bed test of treated brine.

FIG. 30 shows a SEM image from a packed bed test of a 50:50 blend brine.

FIG. 31 shows a SEM image from a packed bed test of a 50:50 blend brine.

FIG. 32 shows TSS by in-line pressure filter of untreated, treated, and50:50 blend brines.

FIG. 33 shows TSS by vacuum filtration of untreated, treated, and 50:50blend brines.

FIG. 34 shows the weight gain of packed bed tubes after the processingof untreated, treated, and 50:50 blend brines.

FIG. 35 shows the porosity change of packed bed tubes after theprocessing of untreated, treated, and 50:50 blend brines.

FIG. 36 shows the concentration of iron and silica in an exemplarytreated brine composition as a function of time during the silicamanagement process.

FIG. 37 shows the concentration of iron and silica in an exemplarytreated brine composition as a function of time during the silicamanagement process.

FIG. 38 shows the concentration of iron and silica in an exemplarytreated brine composition as a function of time during the silicamanagement process.

FIGS. 39A and 39B show histograms of silica concentrations in anexemplary treated brine composition during the silica managementprocess.

FIGS. 40A and 40B show histograms of iron concentrations in an exemplarytreated brine composition during the silica management process.

FIGS. 41A and 41B show histograms of silica concentrations in anexemplary treated brine composition during the silica managementprocess.

FIGS. 42A and 42B show histograms of iron concentrations in an exemplarytreated brine composition during the silica management process.

DETAILED DESCRIPTION OF THE INVENTION

As used herein the following terms shall have the following meanings.

As used herein, “brine” or “brine solution” refers to any aqueoussolution that contains a substantial amount of dissolved metals, such asalkali and/or alkaline earth metal salt(s) in water, wherein theconcentration of salts can vary from trace amounts up to the point ofsaturation. Generally, brines suitable for the methods described hereinare aqueous solutions that may include alkali or alkaline earth metalchlorides, bromides, sulfates, hydroxides, nitrates, and the like, aswell as natural brines. In certain brines, other metals like lead,manganese, and zinc may be present. Exemplary elements present in thebrines can include sodium, potassium, calcium, magnesium, lithium,strontium, barium, iron, boron, silica, manganese, chlorine, zinc,aluminum, antimony, chromium, cobalt, copper, lead, arsenic, mercury,molybdenum, nickel, silver, thallium, vanadium, and fluorine, althoughit is understood that other elements and compounds may also be present.Brines can be obtained from natural sources, such as Chilean brines orSalton Sea brines, geothermal brines, Smackover brines, sea water,mineral brines (e.g., lithium chloride or potassium chloride brines),alkali metal salt brines, and industrial brines, for example, industrialbrines recovered from ore leaching, mineral dressing, and the like. Thepresent invention is also equally applicable to artificially preparedbrine or salt solutions. Brines include continental brine deposits,geothermal brines, and waste or byproduct streams from industrialprocesses, Smackover brines, synthetic brines, and other brinesresulting from oil and gas production. In some embodiments, the brinesare brines from which energy has already been extracted. For instance,brines used herein include brines from which a power plant has alreadyextracted energy through methods such as flashing.

The term “geothermal brine” refers to a saline solution that hascirculated through the crustal rocks in areas of high heat flow and hasbecome enriched in substances leached from those rocks. Geothermalbrines, such as those found in the Salton Sea geothermal fields, caninclude many dissolved metal salts, including alkali, alkaline earth,and transition metal salts.

The term “Salton Sea brine” refers to geothermal brines obtained fromthe geothermal fields in San Diego County, Imperial County, andRiverside County, in California, USA.

The term “treated” in reference to a brine (e.g., “treated brine” or“treated geothermal brine”) refers to brines that have been processedsuch that the concentration of at least one metal or elemental componenthas been reduced in the brine. For instance, a brine in which theconcentration of silica, and iron has been reduced is a treated brine,also referred to as reduced silica and iron brine.

The term “concentrated” in reference to a brine (e.g., “concentratedbrine” or “concentrated geothermal brine”) refers to brines that havereduced water content compared to the original brine. The reduce watercontent brine may be subsequently diluted post concentration to preventsalt precipitation. In some embodiments, concentrated brines can resultfrom evaporative processes.

The term “synthetic brine” refers to a brine that has been prepared suchthat it simulates a naturally occurring brine. For instance, a syntheticbrine can be prepared in an attempt to simulate the brine composition ofvarious geothermal brine reservoirs found in the Salton Sea region(Calif., U.S.). Generally, the synthetic brine simulating a Salton Seageothermal brine has a composition of about 280 ppm lithium, 63,000 ppmsodium, 20,000 ppm potassium, 33,000 ppm calcium, 130 ppm strontium, 700ppm zinc, 1700 ppm iron, 450 ppm boron, 50 ppm sulfate, 3 ppm fluoride,450 ppm ammonium ion, 180 ppm barium 160 ppm silica (reported as SiO₂),and 180,000 ppm chloride. Additional elements, such as manganese,aluminum, antimony, bromine, chromium, cobalt, copper, fluorine, lead,arsenic, mercury, molybdenum, nickel, silver, thallium, and vanadium,may also be present in the brine.

The term “lithium salts” can include lithium nitrates, lithium sulfates,lithium bicarbonate, lithium halides (particularly chlorides andbromides), and acid salts. For example, the Salton. Sea brines havelithium chlorides.

As used herein, precipitates of iron oxides include iron oxides, ironhydroxides, iron oxide-hydroxides and iron oxyhydroxides.

Exemplary embodiments of the present invention include treatedgeothermal brine compositions. In certain embodiments, the compositioncontains a treated geothermal brine having a concentration of silicaranging from 0 to 80 mg/kg and a concentration of iron ranging from 0 to800 mg/kg. In certain embodiments, the composition contains a treatedgeothermal brine having a concentration of silica ranging from 0 to 30mg/kg and a concentration of iron ranging from 0 to 300 mg/kg. Inanother embodiment, the concentration of silica is less than about 5mg/kg, and the concentration of iron is less than about 5 mg/kg in thetreated geothermal brine composition. In another embodiment, theconcentration of silica is less than about 5 mg/kg, and the ironconcentration is less than about 10 mg/kg in the treated geothermalbrine composition. In another embodiment, the concentration of silica isless than about 5 mg/kg, and the iron concentration is less than about100 mg/kg. In another embodiment, the concentration of silica is lessthan about 10 mg/kg, and the iron concentration is less than about 100mg/kg. In another embodiment, the concentration of silica is less thanabout 20 mg/kg, and the iron concentration is less than about 100 mg/kg.In another embodiment, the concentration of silica is less than about 10mg/kg, and the iron concentration is less than about 200 mg/kg. Inanother embodiment, the concentration of silica, is less than about 20mg/kg, and the iron concentration is less than about 200 mg/kg. Inanother embodiment, the concentration of silica, is less than about 30mg/kg, and the iron concentration is less than about 300 mg/kg. Inanother embodiment, the concentration of silica is less than about 40mg/kg, and the iron concentration is less than about 300 mg/kg. Inanother embodiment, the concentration of silica is less than about 40mg/kg, and iron concentration is less than about 200 mg/kg. In anotherembodiment, the concentration of silica is less than about 60 mg/kg, andthe iron concentration is less than about 300 mg/kg. In anotherembodiment, the concentration of silica is less than about 70 mg/kg, andthe iron concentration is less than about 300 mg/kg.

In another embodiment, the treated geothermal brine compositionsdescribed herein have a concentration of arsenic ranging from 0 to 7mg/kg. In another embodiment, the treated geothermal brine compositionsdescribed herein have a concentration of barium ranging from 0 to 200mg/kg. In another embodiment, the treated geothermal brine compositionsdescribed herein have a concentration of lead ranging from 0 to 100mg/kg. In another embodiment, the treated geothermal brine compositionsdescribed herein are Salton Sea brines. In certain embodiments, thetreated geothermal brine is a concentrated geothermal brine.

Also disclosed are exemplary embodiments of methods of using the treatedgeothermal brine compositions described herein. For example withoutlimitations, a treated geothermal brine can be supplied to a process formineral extraction. For example without limitations, the minerals thatcan be extracted from the treated geothermal brine include lithium,manganese, potassium, rubidium, cesium, phosphates, zinc, and lead. Alsodisclosed are exemplary embodiments of methods of using the treatedgeothermal brine compositions described herein that include injectingthe treated geothermal brine compositions into a geothermal reservoir.

Also disclosed are exemplary embodiments of treated Salton Seageothermal brine compositions containing a concentration of silicaranging from 0 to 80 mg/kg and a concentration of iron ranging from 0 to800 mg/kg. Also disclosed are exemplary embodiments of treated SaltonSea geothermal brine compositions containing a concentration of silicaranging from 0 to 30 mg/kg and a concentration of iron ranging from 0 to300 mg/kg. In another embodiment, the treated geothermal brinecompositions described herein have a concentration of arsenic rangingfrom 0 to 7 mg/kg. In another embodiment, the treated geothermal brinecompositions described herein have a concentration of barium rangingfrom 0 to 200 mg/kg. In another embodiment, the treated geothermal brinecompositions described herein have a concentration of lead ranging from0 to 100 mg/kg. In another embodiment, the treated geothermal brinecompositions described herein have a concentration of arsenic less thanabout 7 mg/kg, barium less than about 200 mg/kg, and lead less thanabout 100 mg/kg. In another embodiment, the invention provides ageothermal brine composition having a pH of about 4.0 to about 6.0 thathas less than 20 ppm by weight of silica, less than 20 ppm by weight ofiron, and further wherein the geothermal brine composition has totalsuspended solids (“TSS”) of less than 10 ppm.

In some embodiments, the treated geothermal brine has a concentration ofsilica that ranges from 0 mg/kg to 30 mg/kg. In some embodiments, thetreated geothermal brine has a concentration of silica that is less thanabout 25 mg/kg. In some embodiments, the treated geothermal brine has aconcentration of silica that is less than about 20 mg/kg. In someembodiments, the treated geothermal brine has a concentration of silicathat is less than about 15 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of silica that is less than about12 mg/kg. In some embodiments, the treated geothermal brine has aconcentration of silica that is less than about 10 mg/kg. In someembodiments, the treated geothermal brine has a concentration of silicathat is less than about 8 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of silica that is less than about 5mg/kg. In some embodiments, the treated geothermal brine has aconcentration of silica that is less than about 1 mg/kg. Exemplaryembodiments of the present invention include treated geothermal brinecompositions with reduced concentrations of silica. In an embodiment,the concentration of silica ranges from 0 to 5 mg/kg. In anotherembodiment, the concentration of silica ranges from 0 to 10 mg/kg. Inanother embodiment, the concentration of silica ranges from 0 to 15mg/kg. In another embodiment, the concentration of silica ranges from 0to 20 mg/kg. In another embodiment, the concentration of silica rangesfrom 0 to 25 mg/kg. In another embodiment, the concentration of silicaranges from 0 to 30 mg/kg. In another embodiment, the concentration ofsilica ranges from 0 to 35 mg/kg. In another embodiment, theconcentration of silica, ranges from 0 to 40 mg/kg. In anotherembodiment, the concentration of silica ranges from 0 to 45 mg/kg. Inanother embodiment, the concentration of silica ranges from 0 to 50mg/kg. In another embodiment, the concentration of silica ranges from 0to 55 mg/kg. In another embodiment, the concentration of silica rangesfrom 0 to 60 mg/kg. In another embodiment, the concentration of silicaranges from 0 to 65 mg/kg, in another embodiment, the concentration ofsilica ranges from 0 to 70 mg/kg. In another embodiment, theconcentration of silica ranges from 0 to 75 mg/kg. In anotherembodiment, the concentration of silica ranges from 0 to 80 mg/kg. Inanother embodiment, the concentration of silica, ranges from 0 to 85mg/kg. In another embodiment, the concentration of silica ranges from 0to 90 mg/kg. In another embodiment, the concentration of silica rangesfrom 0 to 95 mg/kg. In another embodiment, the concentration of silicaranges from 0 to 100 mg/kg.

In some embodiments, the treated geothermal brine has a concentration ofiron that ranges from 0 mg/kg to 300 mg/kg. In some embodiments, thetreated geothermal brine has a concentration of iron that ranges from 0mg/kg to 250 mg/kg. In some embodiments, the treated geothermal brinehas a concentration of iron that ranges from 0 mg/kg to 200 mg/kg. Insome embodiments, the treated geothermal brine has a concentration ofiron that ranges from 0 mg/kg to 150 mg/kg. In some embodiments, thetreated geothermal brine has a concentration of iron that ranges from 0mg/kg to 100 mg/kg. In some embodiments, the treated geothermal brinehas a concentration of iron that ranges from 0 mg/kg to 50 mg/kg. Insome embodiments, the treated geothermal brine has a concentration ofiron that ranges from 0 mg/kg to 25 mg/kg. In some embodiments, thetreated geothermal brine has a concentration of iron that ranges from 0mg/kg to 20 mg/kg. In some embodiments, the treated geothermal brine hasa concentration of iron that ranges from 0 mg/kg to 10 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 300 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 250mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 200 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 100 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 75mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 50 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 40 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 30mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 20 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 10 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 9mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 8 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 7 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 6mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 5 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 4 mg/kg. In some embodiments, the treatedgeothermal brine has a concentration of iron that is less than about 3mg/kg. In some embodiments, the treated geothermal brine has aconcentration of iron that is less than about 2 mg/kg. In someembodiments, the treated geothermal brine has a concentration of ironthat is less than about 1 mg/kg.

In some aspects, the invention provides a method for producinggeothermal power using geothermal brines and producing a reduced silicaand iron brine having improved injectivity. The method includes flashinga geothermal brine containing silica and iron to generate electricalpower. This flashing produces precipitated silica and a reduced silicabrine. The precipitated silica is then separated from the reduced silicabrine and returned to the flashing the geothermal brine step. Thereduced silica brine is then exposed to air to facilitate oxidation andto produce precipitated silica and iron solids, and a reduced silica andiron brine. The silica and iron solids are then separated from thereduced silica and iron brine and optionally, at least a portion of thesilica and iron solids are returned to the exposing the reduced silicabrine to air step. The reduced silica and iron treated brine is theninjected into a separate injection well, but the same reservoir, such asa geothermal reservoir, wherein the reduced silica and iron brine hasimproved infectivity as compared to the reduced silica brine. In furtherembodiments, the treated brine having reduced silica, and optionallyiron, concentration is further treated to remove additional components,such as lithium, potassium, rubidium, and/or cesium, selectively or incombination.

In geothermal power plants, heat may be recovered from a geothermalbrine through the use of one or more flash tanks in a process known asflashing. Any method of flashing may be used in the present invention.In some embodiments, the crystallizer reactor clarifier process is used.In other embodiments, the pH modification process is used. In someembodiments, the brine will be treated after it has left the firstclarifier of a two clarifier processing system. In some embodiments, thebrine will be treated after it has been completely processed by theclarifier system.

In some embodiments, the reduced silica and iron brine has aconcentration of silica that ranges from 0 mg/kg to 30 mg/kg. In someembodiments, the reduced silica and iron brine has a concentration ofsilica that is less than 5 mg/kg. In some embodiments, the reducedsilica and iron brine has a concentration of silica that is less than 10mg/kg. In some embodiments, the reduced silica and iron brine has aconcentration of silica that is less than 20 mg/kg. In some embodiments,the reduced silica and iron brine has a concentration of silica that isless than 30 mg/kg.

In some embodiments, the reduced silica and iron brine has less than 20ppm of silica. In some embodiments, the reduced silica and iron brinehas less than 20 ppm of iron. In further embodiments, the reduced silicaand iron brine has less than 20 ppm of silica and less than 20 ppm ofiron. In some embodiments, the reduced silica and iron brine has lessthan 15 ppm of silica. In some embodiments, the reduced silica and ironbrine has less than 15 ppm of iron. Further embodiments, the reducedsilica and iron brine has less than 15 ppm of silica and less than 15ppm of iron. In some embodiments, the reduced silica and iron brine hasless than 10 ppm of silica. In some embodiments, the reduced silica andiron brine has less than 10 ppm of iron. In further embodiments, thereduced silica and iron brine has less than 10 ppm of silica and lessthan 10 ppm of iron. In some embodiments, the reduced silica and ironbrine has less than 5 ppm of silica. In further embodiments, the reducedsilica and iron brine has less than 5 ppm of silica and less than 10 ppmof iron.

In further embodiments of the process, other components may be removedfrom the brine before the brine is injected into an underground region,such as a reservoir. In one embodiment, lithium is removed from thegeothermal brine before the reduced silica and iron brine is injectedinto the underground region. In another embodiment, manganese is removedfrom the reduced silica and iron brine before it is injected into theunderground region. In another embodiment, zinc is removed from thereduced silica and iron brine before it is injected into the undergroundregion. In another embodiment, potassium is removed from the reducedsilica and iron brine before it is injected into the underground region.In another embodiment, rubidium is removed from the reduced silica andiron brine before it is injected into the underground region. In anotherembodiment, cesium is removed from the reduced silica and iron brinebefore it is injected into the underground region. In furtherembodiments, any combination of these components is removed from thereduced silica and iron brine before it is injected into the undergroundregion.

In some embodiments, the reduced silica and iron brine has aconcentration of silica ranging from about 0 mg/kg to about 15 mg/kg, aconcentration of iron ranging from about 0 mg/kg to about 10 mg/kg, anda concentration of potassium ranging from about 300 mg/kg to about 8500mg/kg. In other embodiments, the concentration of silica is less thanabout 10 mg/kg, the concentration of iron of less than about 10 mg/kg,and the concentration of potassium is less than about 4000 mg/kg.

In other embodiments, the concentration of silica is less than about 10mg/kg, the concentration of iron is less than about 10 mg/kg, and theconcentration of potassium is less than about 4000 mg/kg. In otherembodiments, the concentration of silica is less than about 5 mg/theconcentration of iron is less than about 10 mg/kg, and the concentrationof potassium is less than about 4000 mg/kg. In other embodiments, theconcentration of silica is less than about 10 mg/kg, the concentrationof iron is less than about 10 mg/kg, and the concentration of potassiumis less than about 1000 mg/kg. In other embodiments, the a concentrationof silica is less than about 10 mg/kg, the concentration of iron is lessthan about 5 mg/kg, and the concentration of potassium is less thanabout 1000 mg/kg. In other embodiments, the a concentration of silica isless than about 5 mg/kg, the concentration of iron is less than about 10mg/kg, and the concentration of potassium is less than about 1000 mg/kg.In other embodiments, the a concentration of silica is less than about20 mg/kg, the concentration of iron is less than about 10 mg/kg, and theconcentration of potassium is less than about 1000 mg/kg. In otherembodiments, the concentration of silica is less than about 10 mg/kg,the concentration of iron is less than about 10 mg/kg, and theconcentration of potassium is less than about 500 mg/kg. In otherembodiments, the concentration of silica is less than about 5 mg/kg, theconcentration of iron is less than about 10 mg/kg, and the concentrationof potassium is less than about 500 mg/kg.

In further embodiments, the treated geothermal brine composition has aconcentration of silica ranging from about 0 mg/kg to about 15 mg/kg. Inother embodiments, the treated geothermal brine composition has a silicaconcentration of less than about 0 mg/kg. In other embodiments, thetreated geothermal brine composition has a silica concentration of lessthan about 5 mg/kg. In other embodiments, the treated geothermal brinecomposition has a silica concentration of less than about 10 mg/kg. Inother embodiments, the treated geothermal brine composition has a silicaconcentration of less than about 15 mg/kg.

In further embodiments, the geothermal brine has a concentration of ironranging from about 0 mg/kg to about 10 mg/kg. In other embodiments, thetreated geothermal brine composition has an iron concentration of about0 mg/kg. In other embodiments, the treated geothermal brine compositionhas an iron concentration of less than about 5 mg/kg. In otherembodiments, the treated geothermal brine composition has an ironconcentration of about 10 mg/kg.

In further embodiments, the geothermal brine has a concentration ofpotassium ranging from about 300 mg/kg to about 8500 mg/kg. In otherembodiments, the treated geothermal brine composition has a potassiumconcentration of less than about 300 mg/kg. In other embodiments, thetreated geothermal brine composition has a potassium concentration ofless than about 500 mg/kg. In other embodiments, the treated geothermalbrine composition has a potassium concentration of less than about 1000mg/kg. In other embodiments, the treated geothermal brine compositionhas a potassium concentration of less than about 4000 mg/kg. In otherembodiments, the treated geothermal brine composition has a potassiumconcentration of less than about 8500 mg/kg.

In other embodiments, the treated geothermal brine has a concentrationof rubidium ranging from about 30 mg/kg to about 200 mg/kg. In otherembodiments, the treated geothermal brine composition has a rubidiumconcentration of less than about 200 mg/kg. In other embodiments, thetreated geothermal brine composition has a rubidium concentration ofless than about 150 mg/kg. In other embodiments, the treated geothermalbrine composition has a rubidium concentration of less than about 100mg/kg. In other embodiments, the treated geothermal brine compositionhas a rubidium concentration of less than about 50 mg/kg.

In further embodiments, the treated geothermal brine has a concentrationof silica ranging from about 0 mg/kg to about 15 mg/kg, a concentrationof iron ranging from about 0 mg/kg to about 10 mg/kg, and aconcentration of rubidium ranging from about 30 mg/kg to about 200mg/kg.

Embodiments of the present invention yield treated brines with improvedinjectivity over untreated brines solutions. Injectivity is defined interms of change in pressure over a given flow rate over time.Improvements in injectivity indicate that a brine is able to flow morefreely over time, and thus will lead to less required cleanings of awell. One way to assess improved injectivity is through packed bedtesting.

In another aspect, the invention provides a method for preventing silicascale in geothermal brine injection wells and improving injectivity of atreated aqueous brine solution by selectively removing silica and ironfrom a geothermal brine solution. The method includes obtaining ageothermal brine solution comprising silica and iron from a geothermalreservoir. The geothermal brine solution is then supplied to a silicamanagement process to produce a reduced silica geothermal brine solutionrelative to the geothermal brine solution. The reduced silica geothermalbrine solution is then supplied to an iron removal process to produce atreated aqueous brine solution relative to the reduced silica geothermalbrine solution. The treated aqueous brine product solution is theninjected into the geothermal reservoir. The treated brine also has apacked bed test result that yields an operation time at least 50%greater than an operation time of the geothermal brine solution.

In some embodiments, the step of supplying the geothermal brine solutionto a silica management process and the step of supplying the reducedsilica geothermal brine solution to an iron removal process are the samestep. In other embodiments, the step of supplying the geothermal brinesolution to a silica management process and the step of supplying thereduced silica geothermal brine solution to an iron removal process aredifferent steps.

In further embodiments, the treated brine is further treated to removelithium, potassium, rubidium, and/or cesium. In some embodiments, theprocess for removing lithium, potassium, rubidium, and/or cesium occursafter the geothermal brine is supplied to a silica management step. Insome embodiments, the process for removing lithium, potassium, rubidium,and/or cesium occurs after the geothermal brine is supplied to a silicamanagement step. In some embodiments, the process for removingpotassium, rubidium, and/or cesium occurs after the geothermal brine issupplied to both a silica management step and an iron removal process.

In some embodiments, the treated brine has a packed bed test result thatyields an operation time at least 100% greater than an operation time ofthe geothermal brine solution. In some embodiments, the treated brinehas a packed bed test result that yields an operation time at least 200%greater than an operation time of the geothermal brine solution. In someembodiments, the treated brine has a packed bed test result that yieldsan operation time at least 300% greater than an operation time of thegeothermal brine solution.

In another aspect, the invention provides a method for preventing silicascale in geothermal brine injection wells and improving injectivity of atreated brine by selectively removing silica and iron from a geothermalbrine solution. The method includes obtaining a geothermal brinesolution comprising silica and iron from a geothermal reservoir. Thegeothermal brine solution is supplied to a silica management process toproduce a reduced silica geothermal brine solution relative to thegeothermal brine solution. The reduced silica geothermal brine solutionis supplied to an iron removal process to produce a treated brine. Thetreated brine is then injected into the geothermal reservoir.Additionally, the treated brine has a TSS of less than about 60 ppm.

In some embodiments, the treated brine has a TSS of less than about 55ppm. In some embodiments, the treated brine has a TSS of less than about50 ppm. In some embodiments, the treated brine has a TSS of less thanabout 45 ppm. In some embodiments, the treated brine has a TSS of lessthan about 40 ppm. In some embodiments, the treated brine has a TSS ofless than about 35 ppm.

In some embodiments, the treated brine has a TSS of less than about 30ppm. In some embodiments, the treated brine has a TSS of less than about25 ppm. In some embodiments, the treated brine has a TSS of less thanabout 20 ppm. In some embodiments, the treated brine has a TSS of lessthan about 15 ppm. In some embodiments, the treated brine has a TSS ofless than about 10 ppm.

In another aspect, the invention provides a method for generating energyfrom a geothermal brine solution and improving injectivity of a treatedaqueous brine solution by selectively removing silica and iron from ageothermal brine solution used for energy production. The methodincludes obtaining a geothermal brine solution comprising silica andiron from a geothermal reservoir. The geothermal brine solution is thenflashed to produce and recover heat and energy therefrom and to producea spent geothermal brine solution. The spent geothermal brine solutionis then supplied to a silica management process to produce a reducedsilica geothermal brine solution relative to the spent geothermal brinesolution. The reduced silica geothermal brine solution is then suppliedto an iron removal process to produce a treated aqueous brine solutionrelative to the reduced silica geothermal brine solution. The treatedaqueous brine product solution is then injected into the geothermalreservoir. Additionally, the treated brine has a TSS of less than about60 ppm.

In some embodiments, the step of supplying the geothermal brine solutionto a silica management process and the step of supplying the reducedsilica geothermal brine solution to an iron removal process are the samestep. In other embodiments, the step of supplying the geothermal brinesolution to a silica management process and the step of supplying thereduced silica geothermal brine solution to an iron removal process aredifferent steps.

In further embodiments, the treated brine is further treated to removelithium, potassium, rubidium, and/or cesium. In some embodiments, theprocess for removing lithium, potassium, rubidium, and/or cesium occursafter the geothermal brine is supplied to a silica management step. Insome embodiments, the process for removing lithium, potassium, rubidium,and/or cesium occurs after the geothermal brine is supplied to a silicamanagement step. In some embodiments, the process for removingpotassium, rubidium, and/or cesium occurs after the geothermal brine issupplied to both a silica management step and an iron removal process.

In some embodiments, the treated brine has a TSS of less than about 55ppm. In some embodiments, the treated brine has a TSS of less than about50 ppm. In some embodiments, the treated brine has a TSS of less thanabout 45 ppm. In some embodiments, the treated brine has a TSS of lessthan about 40 ppm. In some embodiments, the treated brine has a TSS ofless than about 35 ppm. In some embodiments, the treated brine has a TSSof less than about 30 ppm. In some embodiments, the treated brine has aTSS of less than about 25 ppm. In some embodiments, the treated brinehas a TSS of less than about 20 ppm. In some embodiments, the treatedbrine has a TSS of less than about 15 ppm. In some embodiments, thetreated brine has a TSS of less than about 10 ppm.

In another aspect, the invention provides a treated geothermal brinecomposition having a pH of about 4.0 to about 6.0 that has less thanabout 20 ppm by weight of silica, less than about 20 ppm by weight ofiron, and further wherein the treated geothermal brine composition hasTSS of less than about 30 ppm. In some embodiments, the treatedgeothermal brine composition has a TSS of less than about 25 ppm. Insome embodiments, the treated geothermal brine composition has a TSS ofless than about 20 ppm. In some embodiments, the treated geothermalbrine composition has a. TSS of less than about 15 ppm. In someembodiments, the treated geothermal brine composition has a TSS of lessthan about 10 ppm.

Packed Bed Testing

The objective of packed bed testing is to simulate injectivity of brinesolutions. This entails pumping a brine solution through a material thatsimulates the region where the brine is to be injected. Incompatibilityis primarily manifested as a shorter run time to reach a 1000 maximumpsi, due to generation of suspended solids and scales that cause anincrease in pressure across the packed bed.

In general, the packed beds should be selected such that granulatedmaterials, such as rock chips, may be packed within the inner region,and such that the flow of brine may be allowed continuously over thegranulated materials under pressures up to at least 1000 psig andtemperatures ranging from about 80 to 110° C. The primary responsefactor for the packed bed testing is the time period, or operation time,that the brine is able to be pumped through the packed bed, untilscaling and blockage cause the head pressure to reach 1000 psi.Long-term permeable flow is desired, so the longer the packed bed unitruns, the better the potential outcome of the brine for injecting into areservoir. In some embodiments, the brine can be injected into thereservoir from which it was obtained (also sometimes referred to as“reinjecting”). In some embodiments, the brine can be injected into adifferent reservoir than the one from which it was obtained.

In some embodiments, the beds are packed with screened drilling rockchips from the well hydrothermal zone (e.g., from the well into whichthe brine will be injected). In some embodiments, the rock chips may beprimarily of two types: 1) hydrothermally-crystallized fine-grainedgranitic material composed of quartz and feldspar, and 2) silica-bondedmeta-siltstone. In some embodiments, the packed beds may be acombination of the two types of rock chips. In other embodiments, thepacked beds may be primarily of a single type of rock chip. In someembodiments, the packing material is uniform in size.

In order to yield appropriate comparisons, the same type of material andpacking should be used in both packed bed tests (i.e., for the treatedand untreated brine) for the comparative testing. The packed beds willhave brine pumped through them until the pressure reaches about 1000psig at 1 LPM brine flow. Thus, the materials for the packed beds shouldbe selected from materials that will allow for such pressures andtemperatures ranging from about 80 to 110° C. By comparing the packedbed tests of a treated and an untreated brine, one can assess whetherthe treatment process used has improved injectivity and reduced scaling.If a treated brine has a longer operation time, or the time to reach1000 psi, then the treated brine will have improved injectivity. In someembodiments, the treated brine has an operation time at least about 50%greater than the operation time of the untreated brine solution. In someembodiments, the treated brine has an operation time at least about 100%greater than the operation time of the untreated brine solution. In someembodiments, the treated brine has an operation time at least about 150%greater than the operation time of the untreated brine solution. In someembodiments, the treated brine has an operation time at least about 200%greater than the operation time of the untreated brine solution. In someembodiments, the treated brine has an operation time at least about 250%greater than the operation time of the untreated brine solution. In someembodiments, the treated brine has an operation time at least about 300%greater than the operation time of the untreated brine solution.

TSS is also an important parameter for assessing brines. TSS canindicate whether brines may have minerals that could precipitate solidsand generate suspended solids, contributing to scaling and plugging. Insome embodiments, the TSS of the treated brine will be less than about60 ppm. In some embodiments, the TSS of the treated brine will be lessthan about 30 ppm. In some embodiments, the TSS of the treated brinewill be less than about 25 ppm. In some embodiments, the TSS of thetreated brine will be less than about 20 ppm. In some embodiments, theTSS of the treated brine will be less than about 15 ppm. In someembodiments, the TSS of the treated brine will be less than about 10ppm.

Broadly, also described herein are methods for the selective removal ofsilica and silicates (typically reported as silicon dioxide (SiO₂)) fromsolution. Methods for the removal of silica are commonly known as silicamanagement. As used herein, the selective removal of silica generallyrefers to methods to facilitate the removal of silica from solutions,such as geothermal brines, Smackover brines, synthetic brines, and otherbrines resulting from oil and gas production without the simultaneousremoval of other ions. In certain embodiments, silica is preferablyselectively removed such that the silica can be further refined orsupplied to an associated process, without the need for extensivepurification thereof. In some embodiments, the brines are brines fromwhich energy has already been extracted. For instance, brines from whicha power plant has already extracted energy through methods such asflashing. Broadly described, in certain embodiments, the methodsdescribed herein employ chemical means for the separation of silica. Theremoval of silica from solutions, such as geothermal brines, canprevent, reduce or delay scale formation as silica present in brines canform scale deposits. It is known that scale deposit formation is acommon problem with geothermal brines and therefore the methodsdescribed herein for the selective removal of silica can be utilized toprevent scale formation in geothermal power equipment and also improveinjectivity of treated brines in reservoirs. Additionally, the removalof silica from solutions, such as geothermal brines, also facilitatesthe subsequent recovery of various metals from the solution, such aslithium, manganese, zinc, as well as boron, cesium, potassium, rubidium,and silver. It is understood that the recovery of valuable metals from ageothermal brine depends upon the concentration of a metal in the brine,and the economics of the recovery thereof which can vary widely amongbrines. The prevention, reduction, and/or delay of scale production ingeothermal wells and geothermal power plant equipment can result inincreased geothermal energy production by improving the equipmentlifetime and reducing the frequency of equipment maintenance, as well asincrease or prolong well permeability.

Typically, in geothermal power plants, heat is recovered from ageothermal brine through the use of one or more flash tanks. In certainembodiments, a silica precipitate seed can be supplied to the geothermalbrine prior to the brine being supplied to the flash tanks to remove atleast a portion of the silica present. In other embodiments, thepost-flash geothermal brine from a geothermal plant is then fed throughthe silica management and iron removal steps. In certain embodiments,the silica precipitate seed can result in the removal of up to 25% ofthe silica present in the brine, alternatively up to about 40% of thesilica present in the brine, alternatively up to about 50% of the silicapresent in the brine, alternatively up to about 60% of the silicapresent in the brine, or alternatively greater than about 60% of thesilica present in the brine. In certain embodiments, the silicaprecipitate seed can reduce the silica concentration of the brine toless than about 200 ppm, alternatively less than about 175 ppm,alternatively less than about 160 ppm, alternatively less than about 145ppm.

The geothermal brine supplied to the flash tanks is typically suppliedat a temperature of at least about 250° C., alternatively at least about300° C. After flashing of the geothermal brine and the recovery ofsignificant heat and energy therefrom, the geothermal brine can besupplied to a silica management process (as further described herein)for the removal of additional silica. As noted previously, the removalof silica, can prevent, reduce, or delay the buildup of scale, therebyincreasing the lifetime of the equipment and improving injectivity ofthe treated brine. Typically, the temperature of the brine has beenreduced to less than about 150° C. before it is supplied to one of thesilica removal processes described herein, alternatively less than about125° C., alternatively less than about 120° C., alternatively less thanabout 115° C., alternatively less than about 110° C., alternatively lessthan about 105° C., or alternatively less than about 100° C.

While the removal of silica from geothermal brines in geothermal powerplants is useful for reducing scale buildup in the power plant,supplying the brine to one or more of the silica removal processesdescribed herein also has the effect of reducing the injectiontemperature of the brine to less than about 100° C., alternatively lessthan about 90° C., alternatively less than about 80° C., alternativelyless than about 75° C.

As described herein, the selective silica recovery of the presentinvention can include the use of activated alumina, aluminum salts (suchas AlCl₃), or iron (III) oxyhydroxides.

In certain embodiments of the present invention, the brine or silicacontaining solution can first be filtered or treated to remove solidspresent prior to the selective recovery and removal of silica.

Simulated brines can be prepared to mimic naturally occurring brines. Asdescribed herein, a simulated brine can be prepared to mimic the brinecomposition of various test wells found in the Salton Sea geothermalfields (Calif., U.S.). Generally, the simulated brine is an aqueoussolution having a composition of about 260 ppm lithium, 63,000 ppmsodium, 20,100 ppm potassium, 33,000 ppm calcium, 130 ppm strontium, 700ppm zinc, 1700 ppm iron, 450 ppm boron, 54 ppm sulfate, 3 ppm fluoride,450 ppm ammonium ion, 180 ppm barium, 160 ppm silicon dioxide, and181,000 ppm chloride. Additional elements, such as manganese, aluminum,antimony, chromium, cobalt, copper, lead, arsenic, mercury, molybdenum,nickel, silver, thallium, and vanadium, may also be present in thebrine. It is understood, however, that the methods described herein canbe used to remove silica from brines and other silica containingsolutions having silica concentrations greater than about 160 ppm. Incertain embodiments, the brine or silica containing solution can have asilica concentration of greater than about 400 ppm, greater than about500 ppm, or greater than about 600 ppm. In certain instances, geothermalbrines can have silica concentrations of between about 400 and 600 ppm.

Selective Silica Recovery by Precipitation with Aluminum Salts

The addition of aluminum salts, such as AlCl₃, to brine at a pH ofbetween about 4 and 6, results in the formation of charged polymers,such as Al₁₃O₄(OH)₂₄ ⁷⁺. These charged polymers are highly reactive withrespect to silica, resulting in the formation of amorphousaluminosilicate precipitates, which can be removed by filtration. Incertain embodiments, any silica present in the brine will react with thepositively charged polymer to form an amorphous aluminosilicateprecipitate, thereby reducing the silica concentration of the brine. Incertain embodiments, the brine can be seeded with an aluminosilicateprecipitate, which allows the silica to attach to the seed material,thereby allowing the silica and aluminum polymer to be removed byconventional filtration or clarification processes. Typically, thealuminum polymers do not react with other components in the brine, suchas lithium or iron, and thus they stay in solution while the silicaforms the precipitate.

Silica can be selectively recovered from silica containing solutions(including brines) by contacting them with aluminum salts, particularlyaluminum halides, such as chlorides and bromides and maintaining a pH ofbetween about 4 and 6, preferably between about 4.5 and 5.5, morepreferably between about 4.75 and 5.25, and even more preferably betweenabout 4.85 and 5.15. Generally, the brine solution, as prepared, has ameasured pH of between about 5.1 and 5.3, which is comparable to thebrines of the Salton Sea, which typically have a measured pH of betweenabout 4.9 and 5.1. Aluminum salt is added in a molar ratio of aluminumsalt to silica of at least about 0.25:1, preferably at least about0.5:1, and more preferably at least about 1:1. In certain embodiments,the aluminum salt to silica ratio is between about 0.5:1 and 2:1.Optionally, the solution can be maintained at elevated temperatures. Incertain embodiments, the solution can be at a temperature greater thanabout 50° C., more preferably at least about 75° C., and even morepreferably at least about 90° C. Optionally, the silica containingsolution is seeded with between about 0.1 and 10% by weight of anamorphous aluminosilicate solid. In certain embodiments, the solution isseeded with between about 1 and 2% by weight of the amorphousaluminosilicate solid. In certain other embodiments, the solution isseeded with between about 1.25 and 1.75% by weight of the amorphousaluminosilicate solid.

The addition of, for example, aluminum chloride to an aqueous silicasolution, such as brine, typically lowers the pH (i.e., acidifies) ofthe silica containing solution as the addition results in the productionof aluminum hydroxide and hydrochloric acid. Typically, the pH ismonitored during the process to maintain the solution at a constant pH.In certain embodiments, a base (for example, but not limited to, sodiumhydroxide, calcium hydroxide, and the like) can be added to the silicacontaining solution to maintain the pH of the solution between about 4and 6 alternatively, between about 4.5 and 5.5, and preferably at orabout 5.

In certain embodiments, the addition rate of the base is nearstoichiometric. In certain embodiments, the equipment can be designed toinclude control equipment to add the base in a controlled process sothat at least a stoichiometric amount of base is added to the solution,based upon the amount of silica and AlCl₃ present in solution.

In certain embodiments, the amorphous aluminosilicate solid used as theseed material is prepared in a laboratory setting. Aluminum salt can beadded to a concentrated sodium silicate solution that may optionally beheated, neutralized to a pH of between about 4 and 6, and stirred toform a precipitate. The precipitate is collected, washed, and dried.

Precipitation of the amorphous aluminosilicate with an aluminum salt iscapable of removing at least 75% of the silica present in the silicacontaining solution, preferably at least about 90%, and even morepreferably at least about 95% of the silica present in the silicacontaining solution. In certain embodiments, precipitation of silicafrom a silica containing solution with an aluminum salt results in atotal silica concentration in the resulting solution of less than about15 ppm, preferably less than about 10 ppm, and even more preferably lessthan about 5 ppm.

In one embodiment, the resulting amorphous aluminosilicate precipitateis removed from the solution by filtration, dried, and recycled as seedmaterial for subsequent precipitation of silica. In other embodiments,the aluminosilicate precipitate is supplied to a subsequent process forrecovery of silica and/or aluminum.

In certain embodiments, contacting the silica containing solution withan aluminum halide at a pH of between 4 and 6 results in the formationof a gel, which can be subsequently separated from the remaining aqueoussolution by filtration, which can be aided by the use of a centrifuge.

In certain embodiments, precipitation occurs by adding a seed containingsolution to the brine, contacting the mixture with aluminum chloride,and then contacting the resulting mixture with a base, such aslimestone, NaOH or Ca(OH)₂. In other embodiments, the brine is contactedwith AlCl₃, and the resulting mixture is contacted with a base. In yetother embodiments, the brine is contacted with AlCl₃, the mixture isthen contacted with a seed containing solution, and the resultingmixture is then contacted with a base. Finally, in certain embodiments,the brine is first contacted with AlCl₃, then contacted with a base, andthen the resulting mixture is contacted with a seed containing solution.

Referring now to FIG. 1, apparatus 100 for the removal of silica from asilica containing brine is provided. Water is provided via line 102.First water stream 102 is supplied to first mixer 106, where the wateris mixed with base 104, for example NaOH (caustic soda) or Ca(OH)₂(staked lime) or limestone to produce aqueous base stream 108. Firstmixer 106 can include any known means for mixing the base and water toform a homogeneous stream. Second water stream 102″ is supplied tosecond mixer 112 where the water is combined with flocculant 110 toproduce mixed flocculant stream 114. Exemplary flocculants include, butare not limited to, Magnafloc 351, Nalco 9907, 9911, 9913, 8181, 7193,8170, and the like.

Brine 116 is supplied to third mixer 120 where it is combined withaluminum chloride (AlCl₃) containing stream 118 to produce mixed brinestream 122. Aqueous base stream 108 is combined with mixed brine stream122 in fourth mixer 124 to produce basic brine stream 126. Basic brinestream 126 is supplied to fifth mixer 128 where it is combined andintimately mixed with mixed flocculant stream 114 to coagulate at leasta portion of the silica present in brine stream 126 as analuminosilicate solid. Mixed stream 130 with a reduced silica brine andsolids is supplied to clarifier 132 to produce reduced silica brinestream 134 and slurry stream 136, which can include aluminosilicateprecipitate. Clarifier 132 can be a settling tank or like device thatcan be utilized for the separation of a liquid stream from a slurry.Slurry stream 136 can be supplied to filter 138, which separates theslurry into a solid aluminosilicate precipitate, which can be removedvia solid removal line 140, and a precipitate removed treated brinestream 142. Precipitate removed treated brine stream 142 can then berecombined with reduced silica brine stream 134.

Fifth mixer 128 can include multiple stages. In one embodiment, fifthmixer 128 includes three reactor stages wherein the first reactor stageincludes a mixer to facilitate intimate mixing of the brine, and thealuminum salt, to produce a solid aluminosilicate solid. The secondreactor stage can include means for introducing the base, such as NaOHor Ca(OH)₂ to the reaction mixture. The second reactor stage canoptionally include means for determining the pH of the solution, andcontrol means, such as automated valves, operable to control theaddition of the base to the solution to maintain a desired predeterminedpH. In certain embodiments, the second reactor stage can include meansfor adding an aluminum salt to the solution. The third reactor stage caninclude means for stabilizing the pH of the solution, and means forsupplying a buffer to the solution. In certain embodiments, the thirdreactor stage can include means for adding an aluminum salt to thesolution.

Clarifier 132 can be a vessel and can include valves and linesconfigured to facilitate the removal of an aluminosilicate slurry fromthe bottom of the vessel and a low silica concentration brine streamfrom a position at the midpoint or top of the vessel. In certainembodiments, fifth mixer 128 or clarifier 132 can include a line forsupplying a portion of the aluminosilicate precipitate to the basicbrine stream 108 as seed. In certain embodiments, fifth mixer 128 caninclude a line for supplying a low silica concentration brine stream tobrine stream 116.

The mixers used herein can each separately be a series of continuouslystirred reactors. In certain embodiments, fourth mixer 124 can includeat least one pH meter, wherein the feed of the aqueous base stream 108and brine stream 112 are regulated to maintain a desired pH.

Selective Silica Recovery by Precipitation with Iron

In one embodiment, silica can be removed from a brine by contacting thebrine with iron (III) hydroxide at a pH of between about 4.5 and 6,preferably between about 4.75 and 5.5, more preferably between about 4.9and 5.3.

A synthetic brine can be prepared having the approximate compositionprovided herein for the simulated Salton Sea reservoir, and furtherincluding about 1880 ppm manganese. In certain embodiments, the brinewill have an iron (II) salt, such as iron (II) chloride, naturallypresent in a concentration, for example, of greater than about 1000 ppm.In other embodiments, an iron (II) salt or iron (III) hydroxide can beadded to the brine to achieve a certain concentration of iron (II) saltor iron (III) hydroxide relative to the silica or silicon containingcompounds present in the brine. In certain embodiments, the molar ratioof the iron (II) salt or iron (III) hydroxide to silica is at leastabout 1:1, preferably at least about 4:1, more preferably at least about7:1 and even more preferably at least about 10:1.

When the iron in the brine or silica containing solution is iron (II),for example iron (II) chloride, an oxidant can be added to oxidize iron(II) salt to iron (Ill) hydroxide. Exemplary oxidants include hypohalitecompounds, such as hypochlorite, hydrogen peroxide (in the presence ofan acid), air, halogens, chlorine dioxide, chlorite, chlorate,perchlorate and other analogous halogen compounds, permanganate salts,chromium compounds, such as chromic and dichromic acids, chromiumtrioxide, pyridinium chlorochromate (PCC), chromate and dichromatecompounds, sulfoxides, persulfuric acid, nitric acid, ozone, and thelike. While it is understood that many different oxidants can be usedfor the oxidation of iron (II) to iron (III), in an embodiment, oxygenor air is used as the oxidant and lime or a like base is used to adjustand maintain the pH to a range of between about 4 and 7. This pH rangeis selective for the oxidation of the iron (II) salt to iron (III)hydroxide, and generally does not result in the co-precipitation orco-oxidation of other elements or compounds present in the brine. In oneembodiment, the iron JO salt can be oxidized to iron (III) by spargingthe reaction vessel with air. Air can be added at a rate of at leastabout 10 cfm per 300 L vessel, preferably between about 10 and 50 cfmper 300 L vessel. A person of skill in the art will recognize that thecfm rate can be adjusted based on specific operation parameters. It willbe recognized by those skilled in the art that iron (III) hydroxide mayalso have a significant affinity for arsenic (III) and (V) oxyanions,and these anions, if present in the brine, may be co-deposited with thesilica on the iron (III) hydroxide. Thus, in these embodiments, stepsmay have to be employed to remove arsenic from the brine prior to silicamanagement.

In another embodiment, iron (III) hydroxide can be produced by adding asolution of iron (III) chloride to the brine, which upon contact withthe more neutral brine solution, will precipitate as iron (III)hydroxide. The resulting brine may require subsequent neutralizationwith a base to initiate precipitation of the silica. In certainembodiments, iron (III) hydroxide can be contacted with lime to forminsoluble ferric hydroxide solids, which can be adsorbed with silica.

The iron (III) hydroxide contacts the silica present in the brine toform a precipitate. Without being bound to any specific theory, it isbelieved that the silica, or silicon-containing compound attaches to theiron (III) hydroxide. In certain embodiments, the ratio of iron (III)hydroxide to silica is at least about 1:1, more preferably at leastabout 4:1, more preferably at least about 7:1. In other embodiments, theiron (III) hydroxide is present in a molar excess relative to thesilica. The reaction of the iron (III) hydroxide with silica, is capableof removing at least about 80% of the silica present, preferably atleast about 90% of the silica present, and more preferably at leastabout 95% of the silica present, and typically depends upon the amountof iron (III) hydroxide present in the solution.

In certain embodiments, the pH is monitored continually during thereaction of iron (III) with silica and an acid or a base is added, asneeded, to maintain the pH the desired level, for example, between about4.9 and 5.3. In alternate embodiments, a pH of between about 5.1 and5.25 is maintained. In certain embodiments, a pH of about 5.2 ismaintained.

In certain embodiments, the iron (II) salt containing solution issparged with air for a period of at least about 5 minutes, alternatelyat least about 10 minutes, alternately at least about 15 minutes, andpreferably at least about 30 minutes, followed by the addition of abase, such as calcium oxide, calcium hydroxide, sodium hydroxide, or thelike, to achieve the desired pH for the solution. In certainembodiments, the base can be added as an aqueous solution, such as asolution containing between about 10 and 30% solids by weight.

In certain embodiments, a flocculant, such as the Magnafloc® productsfrom Ciba®, for example Magnafloc 351, or a similar flocculant can beadded in the clarification step. The flocculant can be added in anaqueous solution in amounts between about 0.005% by weight and about 1%by weight. The flocculant can be added at a rate of at least 0.001 gpm,preferably between about 0.001 and 1 gpm, based upon a 300 L vessel. Aperson of skill in the art will recognize that the gpm can be adjustedbased on specific operation parameters. In certain embodiments, theflocculant is a non-ionic flocculant. In other embodiments, theflocculant is a cationic flocculant. In certain embodiments, it isbelieved that non-ionic and cationic flocculants may be useful for usewith iron precipitates. In certain embodiments, Cytec Superfloc-Nflocculants, such as the N-100, N-100 S, N-300, C-100, C-110, C-521,C-573, C-577 and C581 may be used for the recovery of iron and silicaprecipitates, according to the present invention. In other embodiments,flocculant products from Nalco, such as CAT-Floc, MaxiFloc, Nalco98DF063, Nalco 1317 Liquid, Nalco 97ND048, Nalco 9907 Flocculant, Nalco73281, and Nalco 9355 may be used with the present invention.

In certain embodiments, a flocculant can be added to the brine, inaddition to the base, to facilitate the production of larger solids foreasier solid/liquid separation. In certain embodiments, iron (III)silicate solids can be added to the solution to increase the rate ofprecipitation of silicates.

Referring now to FIG. 2, apparatus 200 for the removal of silica from asilica containing brine is provided. Water is provided via line 102.First water stream 102 is supplied to first mixer 106, where the wateris mixed with base 104, for example NaOH (caustic soda) or Ca(OH)₂(slaked lime), to produce aqueous base stream 108. First mixer 106 caninclude any known means for mixing the base and water to form ahomogeneous stream. Second water stream 102″ is supplied to second mixer112 where the water is combined with flocculant 110 to produce mixedflocculant stream 114.

Brine 216 is supplied to third mixer 224 where it is combined withaqueous base stream 108 and air 225 to produce mixed brine stream 226,with iron-silica precipitates. Mixed brine stream 226 is supplied tofourth mixer 228 where it is combined and intimately mixed with mixedflocculant stream 114 to further encourage precipitation of at least aportion of the silica present in brine stream 226. Mixed stream 230containing a reduced silica brine and solids is supplied to clarifier232 to produce reduced silica brine stream 234 and slurry stream 236,which can include iron-silica precipitates. Clarifier 232 can be asettling tank or like device that can be utilized for the separation ofa liquid stream from a slurry including a filter such as candle filters.Slurry stream 236 can be supplied to filter 238, which separates theslurry into a solid precipitate, which can be removed via solid removalline 240, and a treated brine stream 242. Solids removed via solidremoval line 240 can optionally be separated from any remaining liquidby centrifugation. Precipitate removed treated brine stream 242 can thenbe recombined with reduced silica brine stream 234. Optionally,precipitate removed treated brine stream 242 can be recycled to thirdmixer 224, or alternatively can be combined with brine stream 226.

Fourth mixer 228 can include multiple stages. In an embodiment, fourthmixer 228 includes three reactor stages wherein the first reactor stageincludes a mixer to facilitate intimate mixing of the brine and air. Insome embodiments, sufficient air is supplied to the reactor to oxidizeat least a portion of the iron (II) present to iron (III). The secondreactor stage can include means for introducing the base, such as NaOHor Ca(OH)₂ to the reaction mixture. The second reactor stage canoptionally include means for determining the pH of the solution, andcontrol means, such as automated valves, operable to control theaddition of the base to the solution to maintain a desired predeterminedpH. In certain embodiments, the third reactor stage can include meansfor adding an aluminum salt to the solution. Optionally, apparatus 200can include means for supplying air to the second and third reactorstages.

In certain embodiments, the brine is supplied to the first reactor stageat a pH of about 4.9 to 5.1 and a temperature of about 95-110° C. whereit is contacted and sparged with air to produce certain iron (III)oxyhydroxides. Preferably, a sparging diffuser is utilized to facilitatecontact between the air and iron (II) contained in the brine. At atemperature of greater than about 90° C., the of the first reactor stageis controlled such that the pH is at least about 2.5, but preferably inthe range of 3.5 to 5.3. The pH is maintained by the addition of time orother base to the reactor to prevent the pH becoming too acidic, whichwould prevent further oxidation of the iron (II) to iron (III).

In certain embodiments, in the second reactor stage, the lime or otherbase is added white continuing to sparge air through the brine. Thisprovokes precipitation of ferric ions as oxides, hydroxides, oroxyhydroxides. Additionally, silica and other metals are adsorbed on thesurface of the iron oxyhydroxides. The metals that adsorb on the ferricoxyhydroxides include arsenic, antimony, lead, and barium. The pH of thesecond stage of the reactor is maintained such that the pH of no greaterthan about 6, alternatively not greater than about 5.4, preferably notabove about 5.3, and more preferably not above about 5.2. Additional aircan be fed to the second reactor stage through a sparger, such as an airdiffuser, to facilitate the preparation and precipitation of iron (III)hydroxides adsorbed with silica.

In certain embodiments, the third reactor stage can serve as a buffertank that is configured to maintain the pH of the solution at a pH of nogreater than about 6, alternatively not greater than about 5.4,preferably not greater than about 5.3, and even more preferably at a pHof not greater than about 5.2. Optionally, the third reactor stage caninclude an air sparger, such as an air diffuser, to facilitatepreparation and precipitation of iron (III) hydroxides adsorbed withsilica.

Clarifier 232 can be a vessel and can include valves and linesconfigured to facilitate the removal of an iron-silica slurry from thebottom of the vessel and a reduced silica concentration brine streamfrom a position at the midpoint or top of the vessel. In certainembodiments, fourth mixer 228 or clarifier 232 can include a line forsupplying a portion of the iron-silica precipitate to the basic brinestream 216 as seed. Alternatively, clarifier 232 can include one or morelines configured to deliver iron (III) hydroxide precipitate materialadsorbed with silica to one or more of the first, second, or thirdreactor stages. In certain embodiments, fourth mixer 228 can include aline for supplying a reduced silica concentration brine stream to basicbrine stream 216.

In certain embodiments, apparatus 200 can include control means forcontrolling the addition of base to third mixer 224. In alternateembodiments, apparatus 200 can include control means for controlling theaddition of base to the second reactor stage.

In certain embodiments, brine stream 216 can be preconditioned bysparging the brine stream with air prior to supplying the brine to thirdmixer 224.

The mixers used herein can each separately be a series of continuouslystirred reactors. In certain embodiments, third mixer 224 can include atleast one pH meter, wherein the feed of the aqueous base stream 108 andbrine stream 216 are regulated to maintain a desired pH.

In certain embodiments, precipitation of silica and iron hydroxide canbe achieved by recycling precipitate from the clarifier 232 to thirdmixer 224, resulting in an increase of the size of ferrosilicateparticles. Additional recycling can also be achieved by recycling theseeds from clarifier 232 to first mixer 106, where base 104 is mixedwith some or all of the seeds to promote the formation of a densifiedseed, which can then be fed to third mixer 224. This recycling step canenhance the quality of the precipitate by increasing density of theprecipitate, thus making the design of clarifier 232 smaller andsimpler. It has also surprisingly been found that on the introduction ofthese solids to the reaction vessel a minor amount of the zinc and/ormanganese is retained in the precipitate. In certain embodiments, whenseeds are re-introduced into third mixer 224, there is no or minimal netloss of zinc and manganese that may be present in the brine, and theability of the ferrosilicate precipitate to grow and capture silica isunimpaired.

The rate of the addition of the air, base, and flocculant is based uponthe size of the reactor and the concentrations of iron and silica.Generally, the rates of addition of the components are proportional tothe other components being added and the size of the reaction vessels.For example, to a geothermal brine having iron and silica present, whichis supplied at a rate of about 6 gpm (gallons per minute) to a silicaremoval process having an overall capacity of about 900 gal., air can beadded at a rate of about 100 cfm, a 20% solution of calcium oxide inwater can be added at a rate of about 0.5 lb/min., and a 0.025% solutionof Magnafloc 351 (flocculant) at a rate of about 0.01 gpm.

Selective Silica Recovery with Activated Alumina

Activated alumina is a known absorbent for silica. In certainembodiments, activated alumina is a mixture of γ-Al₂O₃ and AlO(OH)(boehmite). Specifically, activated alumina has been utilized in theremoval of silica, from raw water, such as water that is fed to aboiler. Activated alumina has not been used for the removal of silicafrom brines, wherein the removal of the silica does not also result inthe removal of other ions or compounds by the activated alumina. Methodshave not been reported for the selective removal of silica from brineswithout concurrent removal of other ions or compounds.

Activated alumina is a known absorbent for organic and inorganiccompounds in nonionic, cationic, and anionic forms. Indeed, activatedalumina is a common filter media used in organic chemistry for theseparation and purification of reaction products.

In another embodiment of the present invention, silica can be removedfrom a brine by contacting the brine with activated alumina at a pH ofbetween about 4.5 and 7, alternatively between about 4.75 and 5.75, orin certain embodiments, between about 4.8 and 5.3. The activated aluminacan have a BET surface area of between about 50 and 300 m²/g. In certainembodiments, the brine can be combined and stirred with activatedalumina to selectively remove the silica. In alternate embodiments, theactivated alumina can be added to the brine and stirred to selectivelyremove silica and silicon containing compounds. In certain embodiments,the pH of the brine can be maintained at between about 4.5 and 8.5,preferably between about 4.75 and 5.75, and more preferably betweenabout 4.8 and 5.3, during the step of contacting the silica with theactivated alumina. In certain embodiments, the pH can be maintained atbetween about 4.75 and 5.25. Alternatively, the pH can be maintained atbetween about 5.25 and 5.75. Alternatively, the pH can be maintained atbetween about 5.75 and about 6.25. A pH meter can be used to monitor thepH before, during, and after the contacting step. In certainembodiments, the pH is controlled by titrating the solution with astrong base, such as sodium hydroxide. In an exemplary embodiment,approximately 0.1M solution of sodium hydroxide is used to adjust the pHof the reaction, although it is understood that a base of higher orlower concentration can be employed.

Regeneration of the activated alumina can be achieved by first washingthe alumina with a base, for example, a sodium hydroxide solution of atleast about 0.01M, followed by the subsequent washing with an acid, forexample, a hydrochloric acid solution of at least about 0.01M. In someembodiments, regeneration can be followed by treatment with a sodiumfluoride solution having a pH of between about 4 and 5, to completelyrecover the capacity of the activated alumina. Optionally, the columncan be rinsed with water, preferably between 1 and 5 volumes of water,prior to contacting with sodium hydroxide.

In certain embodiments, wherein the silica containing solution can becontacted with the activated alumina in a column, the solution exitingthe column can be monitored to determine loading of the activatedalumina.

FIG. 3 details apparatus 300 and shows an embodiment that incorporatesremoval of silica by precipitation with iron, as shown in FIG. 2,followed by removal of any remaining silica by adsorption with activatedalumina. Specifically, low silica brine stream 234 can be supplied tofirst adsorbent column 344, which is charged with activated alumina andis operable to remove at least a portion of the silica present in thelow silica brine stream. Treated stream 346 is then supplied to a secondadsorbent column 348, which is similarly charged with activated aluminaand is operable to remove at least a portion of the silica present inthe treated stream, to produce product stream 350, which has a silicacontent that is lower than that of the low silica brine stream 234. Inembodiments wherein treated stream 346 includes a measurableconcentration of silica, second adsorbent column 348 is operable toproduce a product stream 350 having a lower silica concentration thanthat of the treated stream 346.

Referring to FIG. 4, apparatus 400 for the removal of silica byadsorption with activated alumina is provided. A silica containingsolution or silica containing brine is supplied via line 402 to firstadsorbent column 404, which is charged with activated alumina and isoperable to remove at least a portion of the silica present in the brineor other solution and produce treated stream 406 having a reduced silicacontent relative to that of the stream being fed through line 402.Treated stream 406 can then be supplied to a second adsorbent column408, which can also be charged with an activated at alumina adsorbentthat is operable to remove at least a portion of the silica present intreated stream 406 to produce a product stream 410 having a reducedsilica content relative to the silica containing solution or silicacontaining brine supplied via line 402, and in certain embodiments,relative to treated stream 406.

In certain embodiments, regenerant solution 412 can be supplied to firstadsorbent column 404. Regenerant solution 412 can be a strong base, andcan be supplied to remove silica adsorbed onto the activated alumina.Waste stream 414 is configured to provide means for the removal of theregenerant solution and any silica removed from the activated alumina.Optionally, as noted above, a strong acid can be supplied to firstadsorbent column 404 after the regenerant solution and/or a sodiumfluoride solution can be supplied to the column. While FIG. 4 shows thatregenerant solution 412 is supplied at the bottom of adsorbent column404 and flows in a countercurrent flow, it is understood that theregenerant solution can also be supplied such that it flows in aco-current flow.

In certain embodiments, wash water 416, such as deionized water, can besupplied to adsorbent column 404 and a wash water waste stream 418 canbe removed from the column. While the wash water is shown as beingsupplied in a co-current flow, it is understood that the wash water canbe supplied in a counter-current flow.

In certain embodiments, apparatus 400 can include more than twoadsorbent columns. In certain methods wherein three or more columns areincluded in the apparatus, only two adsorbent columns are utilized atany one time. When the activated alumina of one column begins to loseefficiency (i.e., when silica has become adsorbed to a or portion of theactivated alumina such that the increasing amounts of silica are notremoved by the column), that column can be removed from service and athird column can be employed. When the column is removed from service,it can be regenerated, as described above, and returned to service whenthe efficiency of the second column decreases, thereby indicating theadsorbent in the second column is losing effectiveness. In this manner,apparatus 400 can be run continuously as two columns and can be employedfor the removal of silica while a third column is regenerated.

In certain embodiments, a brine, such as a geothermal brine, can besupplied to a process designed to remove a significant portion ofsilica, and optionally iron, present in the brine as a precursor step tothe subsequent recovery of valuable components, such as potassium,rubidium, cesium, lithium, zinc, and manganese, and other elements.Exemplary methods for the reduction of the silica concentration includethose described herein. The treated brine solution having a reducedsilica concentration can then be supplied to an associated process thatis designed to selectively remove one or more components from thetreated brine. Optionally the process for the removal of silica can alsoinclude the removal of iron.

In certain embodiments, the treated brine can be supplied to a processdesigned to selectively remove and recover lithium. Certain methods forthe recovery are known in the art, such as is described in U.S. Pat.Nos. 4,116,856, 4,116,858, 4,159,311, 4,221,767, 4,291,001, 4,347,327,4,348,295, 4,348,296, 4,348,297, 4,376,100, 4,430,311, 4,461,714,4,472,362, 4,540,509, 4,727,167, 5,389,349, 5,599,516, 6,017,500,6,048,507, 6,280,693, 6,555,078, 8,287,829, 8,435,468, 8,574,519, and8,637,428. Alternatively, methods can be employed utilizing a lithiumaluminate intercalate/gibbsite composite material, a resin based lithiumaluminate intercalate, and a granulated aluminate intercalate asdescribed in U.S. Pat. No. 8,637,428 and U.S. patent application Ser.Nos. 12/945,519 and 13/283,311. Preferably, recovery of lithium occurswithout the co-precipitation of other metals.

For example, as shown in FIG. 5, process 10 for the removal of silicaand iron from brine, followed by the subsequent removal of lithium, isprovided. In an exemplary embodiment, brine 12, having a silicaconcentration of at least about 100 ppm, an iron concentration of atleast about 500 ppm, and a recoverable amount of lithium or other metal,is supplied with air 14, base stream 16, and flocculant stream 18 to asilica removal process 20.

Silica removal process 20 can produce brine solution 26 having a reducedconcentration of silica, and optionally iron, compared to the initialbrine, as well as a reaction by-product stream 24 that includes silicathat was previously present in the geothermal brine. Additionally,air/water vapor are produced and removed via line 22.

The brine solution 26 having a reduced concentration of silica and ironcan be supplied to a lithium recovery process 28. The lithium recoveryprocess can include a column or other means for contacting the brinewith a extraction material suitable for the extraction and subsequentrecovery of lithium. In certain embodiments, the extraction material canbe a lithium aluminate intercalate, an inorganic material with a layeredcrystal structure that is both highly selective for lithium andeconomically viable. Exemplary lithium intercalate materials can includea lithium aluminate intercalate/gibbsite composite material, a resinbased lithium aluminate intercalate and a granulated lithium aluminateintercalate. The gibbsite composite can be a lithium aluminateintercalate that is grown onto an aluminum trihydrate core. Theresin-based lithium aluminate intercalate can be formed within the poresof a macroreticular ion exchange resin. The granulated lithium aluminateintercalate can consist of fine-grained lithium aluminate intercalateproduced by the incorporation of a small amount of inorganic polymer.

The process of contacting the lithium aluminate intercalate materialwith the brine is typically carried out a column that includes theextraction material. The brine flows into the column and lithium ionsare captured on the extraction material, while the water and other ionspass through the column as geothermal brine output stream 34. After thecolumn is saturated, the captured lithium is removed by flowing watersupplied via line 30, wherein the water can include a small amount oflithium chloride present, through the column to produce lithium chloridestream 32. In some embodiments, multiple columns are employed for thecapture of the lithium.

As shown in FIG. 6, a continuous process for the management of silica isprovided. Silica management system 1106 includes three stirred vessels1108, 1110, and 1112 provided in series. To first reactor 1108 isprovided a geothermal brine via line 1104. In some embodiments, thegeothermal brine has an iron content of approximately 1500 ppm and asilica content of about 160 ppm. The brine is added at a rate of about 6ppm. Air is supplied via line 1140 to each reactor 1108, 1110, and 1112and is sparged through the geothermal brine. In some embodiments, theair is supplied at a rate of about 100 cfm. In some embodiments, thebrine supplied to each of the three reactors is maintained at atemperature of about 95° C.

An aqueous calcium oxide slurry is prepared by mixing solid calciumoxide proved from tank 1130 via line 1132 to vessel 1134, where thesolid is mixed with water 1120 provided via line 1122. In someembodiments, the calcium oxide slurry includes between about 15 and 25%by weight, alternatively about 20% by weight, calcium oxide, and issupplied to second reactor 1110 at a rate on a wet basis of about 0.5lb/min.

In silica management system 1106, brine is supplied to first vessel 1108where the brine is sparged with air via line 1140′. The brine is thensupplied from first vessel 1108 to second vessel 1110. The brine insecond vessel 1110 is contacted with calcium oxide supplied via line1136 and is again sparged with air supplied via line 1140″. The brine isthen supplied from second vessel 1110 to third vessel 1112 where it isagain sparged with air supplied via line 1140′″. In some embodiments,the air to the vessels is supplied at a constant rate. In furtherembodiments, the air to the vessels is supplied at a constant rate ofabout 100 cfm.

After the addition of the air via line 1140 to first reactor 1108, thepH drops, in some embodiments, the pH drops to between about 2.3 and3.5. Air is added to second reactor 1110 via line 1140″. In someembodiments, air is supplied at a rate of about 1100 cfm and a charge ofapproximately 15-25% by weight of an aqueous calcium oxide slurry at arate of about 0.5 lb/min., which can raise the pH in the second reactorto between about 4.8 and 6.5, and preferably between about 5.0 and 5.5.The addition of calcium oxide slurry initiates the precipitation of iron(III) hydroxide and iron silicate. In some embodiments, to third reactor1112, air is added via line 1140′″ at a rate of about 100 cfm. Each ofthe three reactors includes means for stirring to ensure sufficientmixing of the brine, base, and air oxidant.

In some embodiments, the continuous addition of air and base to thereaction vessels results in the precipitation of the iron and silica atrates up to about 0.5 lb/min., depending upon the concentration of ironand silica in the geothermal brine.

The geothermal brine, which now includes precipitates of iron (III)hydroxide and iron silicate, is then supplied from third vessel 1112 toclarifier 1146 via line 1144. Water may be added to clarifier 1146 vialine 1122. In some embodiments, an aqueous flocculant solution ofMagnafloc 351, in a concentration between about 0.005% and 1% by weight,such as about 0.025% by weight, is prepared by supplying solidflocculant 1124 via line 1126 to flocculant tank 1128, where the solidis contacted with water 1120 supplied via line 1122. In furtherembodiments, the aqueous flocculant solution is supplied to clarifiervessel 1146 via line 1138 at a rate of about 0.01 gpm.

Two streams are produced from clarifier 1146. First clarifier productstream 1148 includes the geothermal brine having a reduced concentrationof silica and iron, and may be supplied to a secondary process, such aslithium recovery. Second clarifier product stream 1150 includes solidsilica-iron waste, as well as some geothermal brine. Stream 1150 can besupplied to filter process 1156 which serves to separate the solidsilica-iron waste 1160 from the liquid brine 1162. Alternately, aportion stream 1160 can be resupplied (not shown) to second vessel 1110via line 1154.

Alternate processes for the removal of silica can also be employed asdescribed herein.

In certain embodiments, the treated brine solution can be supplied to aprocess designed to selectively remove and recover at least one ofmanganese and zinc. In a first embodiment, the pH of the solution can beadjusted to selectively precipitate zinc and/or manganese. Followingprecipitation of zinc and/or manganese, the solids can be separated fromthe solution by known filtration means.

Separation of the zinc and manganese solids can be achieved bydissolving the solids in acid, followed by selective recovery of eitherzinc or manganese. In certain embodiments, manganese can be oxidized toprecipitate a manganese solid, which can be separated by filtration.Zinc remaining in solution can be recovered by electrochemical means.

Alternatively, zinc and/or manganese can be selectively removed byextraction. In certain embodiments, zinc and manganese can be separatelyrecovered by individual extractions, or by double extraction. In certainembodiments, zinc and manganese can each selectively be recovered byelectrochemical means.

Known methods for the recovery of zinc that can be used for recoveryfrom brine solutions are described in U.S. Pat. Nos. 5,229,003,5,358,700, 5,441,712, 6,458,184, 8,454,816, and 8,518,232.

Known methods for the recovery of manganese that can be used forrecovery from brine solutions are described in U.S. Pat. Nos. 6,682,644,8,454,816, 8,518,232, and U.S. Patent Publication Nos. 2003/0226761 and2004/0149590.

FIGS. 7, 8, and 9 show exemplary embodiments of the present invention.FIG. 7 is an illustration of an exemplary embodiment of power productionusing a geothermal brine, followed by silica management. The brine 3101is taken from a reservoir and supplied to a high pressure separator3102. From the high pressure separator are produced two streams, hotbrine 3104 and steam 3103. The steam 3103 is then fed to a condenser3105 to remove salts and entrained water whereby high pressure steam3106 is generated and fed to a turbine/generator 3107 to produce energy3108. An acid 3109, preferably hydrochloric acid, is added to the hotbrine 3104, as the brine is a chloride brine. Other acids also can beused. The acid/hot brine stream 3110 is then fed to a standard pressureseparator 3111. Two streams are produced from the standard pressureseparator, a standard pressure steam 3112 and return brine 3113. Thestandard pressure steam 3112 is then fed to a condenser 3114 to removeentrained brine whereby clean standard pressure steam 3115 is generatedand fed to turbine/generator 3107 to produce energy 3108. The returnbrine 3113 is fed to an iron-silica removal process 3116 whereby ironand silica are removed from the brine by addition of a base 3117 and anoxidant 3118 to produce a reduced silica and iron silica brine stream3119. The reduced silica and iron brine stream can optionally be fed toa mineral extraction process 3120 whereby at least one mineral isremoved from the reduced silica and iron brine stream. The reducedsilica and iron brine stream 3121 is then injected into a reservoir3122.

FIG. 8 is an illustration of an exemplary embodiment of power productionusing a geothermal brine, followed by silica management. The brine 3201is taken from a reservoir and supplied to a high pressure separator3202. From the high pressure separator 3202 are produced two streams,high pressure steam 3203 and concentrated brine stream 3204. The highpressure stream 3203 is then fed to a turbine/generator 3205 to produceenergy 3206. The concentrated brine stream 3204 is then fed to a highpressure crystallizer 3207 to produce a stream 3208 that is fed to a lowpressure crystallizer 3210. A high pressure steam 3209 is generated andfed to a turbine/generator 3205 to produce energy 3206. From the lowpressure crystallizer 3210 is produced a low pressure steam 3211 thatfed to the turbine/generator 3205 to produce electricity 3206 and astream 3212 that is fed to a flash tank 3213. From the flash tank 3213are produced two streams, low pressure steam 3214 that is fed to aturbine 3205 and a stream of brine and silica solids 3215 that are fedto a primary clarifier 3216. From the primary clarifier 3216, seeds 3217are recycled to the high pressure crystallizer 3207 and brine 3218 isfed to a silica, management process 3219 to remove silica by addition ofa base 3220 and an oxidant 3221. Optionally, iron may be removed, aswell. From the silica management process 3219, a reduced silica (andoptionally reduced iron) brine 3222 is then fed to a secondary clarifier3223 to remove silica. From the secondary clarifier 3223 the stream 3224is fed to an optional metal recovery process 3225. Seeds 3226 are alsorecycled from the secondary clarifier 3223 to the high pressurecrystallizer 3207. The reduced silica and optionally reduced iron) brine3227 is then injected into a reservoir. Stream 3228 can be supplied tofilter process 3229, which serves to separate the solid silica-ironwaste 3230 from the liquid brine 3228. Alternately, stream 3231 can beresupplied to second clarifier 3223.

Similarly, FIG. 9 is an illustration of an exemplary embodiment of powerproduction using a geothermal brine, followed by silica management. Thebrine 3301 is taken from a reservoir and supplied to a high pressureseparator 3302. From the high pressure separator 3302 are produced twostreams, high pressure steam 3303 and concentrated brine stream 3304.The high pressure steam 3303 is then fed to a turbine/generator 3305 toproduce energy 3306. The concentrated brine stream 3304 is then fed to ahigh pressure crystallizer 3307 to produce a stream 3308 that is fed toa low pressure crystallizer 3310. A high pressure steam 3309 isgenerated and fed to a turbine/generator 3305 to produce energy 3306.From the low pressure crystallizer 3310 is produced a low pressure steam3311 that is fed to the turbine/generator 3305 to produce electricity3306 and a stream 3312 that is fed to a flash tank 3313. From the flashtank 3313 are produced two streams, a low pressure steam 3314 that isfed to a turbine 3305, and a stream of brine and silica solids 3315 thatis fed to a primary clarifier 3316. From the primary clarifier 3316,seeds 3317 are recycled to the high pressure crystallizer 3307, and thebrine 3318 is fed to a secondary clarifier 3319. While the primaryclarifier 3316 removes the bulk of the solids, the secondary clarifier3319 can further reduced the TSS. From the secondary clarifier 3319, twostreams are produced. One stream 3320 is fed in part to a filter 3321 oralternative solids liquid separator where silica solids 3322 areremoved. The brine containing silica and iron 3323 is fed to a silicamanagement process 3324, which receives base 3325 and oxidant 3326.Optionally, iron can be removed as well. In some embodiments, the brinecontains about 160 ppm silica and about 1600 to 2000 ppm of iron. Thereduced silica (and optionally reduced iron) brine 3327 may be fed to anoptional metal recovery process 3328. The reduced silica (and optionallyreduced iron) brine is then injected into a reservoir 3329. Stream 3330can be supplied to filter process 3331 which serves to separate thesolid waste 3332.

In further embodiments, the reduced silica (and optionally reduced iron)brine is then supplied to a process for the selective removal oflithium, potassium, rubidium and/or cesium.

Selective Removal of Potassium, Rubidium, and/or Cesium from Brines

Broadly described herein are methods of removing potassium, rubidium,and/or cesium, selectively or in combination, from brines. In someembodiments, the methods are operable to remove potassium, rubidium,and/or cesium, selectively or in combination, from brines that havealready been treated to remove silica. In further embodiments, themethods are operable to remove potassium, rubidium, and/or cesium,selectively or in combination, from brines that have already beentreated to remove silica and iron. As shown in FIG. 10, by process 3400of the present invention, a heated brine that contains potassium,rubidium, and/or cesium ions is contacted with a tetrafluoroboratecontaining solution to produce potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate precipitate in step3410. In certain embodiments, the brine is heated to a temperature ofbetween about 70 to 100° C., in order to facilitate the reactivity ofthe potassium, rubidium, and/or cesium ions in the brine. In otherembodiments, the brine is heated to a temperature of between about 80 to100° C. In some embodiments, the brine solution is heated to atemperature of about 70° C. In some embodiments, the brine solution isheated to a temperature of about 75° C. In some embodiments, the brinesolution is heated to a temperature of about 80° C. In some embodiments,the brine solution is heated to a temperature of about 85° C. In someembodiments, the brine solution is heated to a temperature of about 90°C. In some embodiments, the brine solution is heated to a temperature ofabout 95° C. In some embodiments, the brine solution is heated to atemperature of about 100° C.

In certain embodiments, the tetrafluoroborate compound is an acid orsalt that includes tetrafluoroborate anions. Exemplary tetrafluoroboratecompounds include fluoroboric acid, ammonium tetrafluoroborate, alkalimetal tetrafluoroborates, and alkaline earth metal tetrafluoroboratesalthough it is understood that other compounds can also be used.

In some embodiments, the brine is contacted with the tetrafluoroboratecompound in an amount between about 10 to 80 grams per liter of brine.In some embodiments, the brine is contacted with the tetrafluoroboratecompound in an amount between about 15 to 60 grams per liter of brine.In some embodiments, the brine is contacted with the tetrafluoroboratecompound in an amount between about 35 to 80 grams per liter of brine.In some embodiments, the brine is contacted with the tetrafluoroboratecompound in an amount of at least about 10 grams per liter of brine. Instep 3410, the brine and the tetrafluoroborate compound are contactedfor between about 30 to 60 seconds. In certain embodiments, thetetrafluoroborate compound and the brine are vigorously mixed. In oneembodiment, after the tetrafluoroborate compound has been added to thebrine, the mixture is placed in a centrifuge for between about one tofive minutes. The centrifuge speed is between about 1000-5000revolutions per minute, alternatively at a speed of at least 4000revolutions per minute. Following centrifugation of the mixture, aprecipitate layer that includes potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate and an aqueous layerwill be present. The potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate precipitate layer3420 and the aqueous layer is separated using techniques known in theart. In certain embodiments, after separation, the precipitate layercontaining potassium tetrafluoroborate, rubidium tetrafluoroborate,and/or cesium tetrafluoroborate is then washed with water. In certainembodiments, the use of fluoroboric acid as the tetrafluoroboratecompound selectively precipitates at least about 95% of the potassiumpresent in the brines. As an example, the reaction for a brinecontaining potassium chloride, which is contacted with a sodiumtetrafluoroborate solution is shown in Equation 1 below.KCl_((aq))+NaBF_(4(aq))→KBF_(4(s))+NaCl_((aq))  Eq. 1Preparation of Potassium Chloride, Rubidium Chloride, and/or CesiumChloride Using Ionic Liquids

In another embodiment of the invention, a method for the preparation ofpotassium chloride, rubidium chloride, and/or cesium chloride,selectively or in combination, from potassium tetrafluoroborate,rubidium tetrafluoroborate, and/or cesium tetrafluoroborate using ionicliquids is provided. In step 3430, potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is supplied to anionic liquid solution that contains chloride anions. In certainembodiments of the invention, the potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is prepared using themethod described above. In some embodiments, the ionic liquid solutionis selected from the group consisting of quaternary ammonium chlorides.In other embodiments, the ionic liquid solution is selected from a groupof phosphonium chlorides. Exemplary ionic liquid solutions includetetrabutylammonium chloride (IRAQ and trihexyltetradecyl phosphoniumchloride.

In some embodiments, potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is added to the ionicliquid solution in an amount between about 35 to 80 grams per liter ofbrine. In some embodiments, potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is added to the ionicliquid solution in an amount between about 10 to 80 grams per liter ofbrine. The ionic liquid solution and potassium tetrafluoroborate,rubidium tetrafluoroborate, and/or cesium tetrafluoroborate mixture isthen heated until the potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is dissolved. Incertain embodiments, the mixture is heated to a temperature of betweenabout 70 to 100° C. alternatively between about 80 to 100° C. andalternatively to about 90° C. In some embodiments, the mixture isstirred during the heating step. In exemplary embodiments, whenutilizing quaternary ammonium chloride ionic liquids, the stirring isdone intermittently, as may be necessary to dissolve all of thepotassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate. In exemplary embodiments that employ phosphoniumchloride ionic liquids, the stirring is vigorous and employed forbetween about 20 and 30 minutes.

After heating the ionic liquid to dissolve the potassiumtetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate, the mixture separates into two distinct layers. Incertain embodiments using quaternary ammonium chloride ionic liquids,separation of the two layers includes a light white solid precipitatelayer that is on top of an aqueous layer. The aqueous layer in theseembodiments includes potassium chloride, rubidium chloride, and/orcesium chloride. In certain embodiments using phosphonium chloride ionicliquids, the two layers include an organic layer and an aqueous layer.The aqueous layer in these embodiments includes potassium chloride,rubidium chloride, and/or cesium chloride. Equation 2 is an exemplaryreaction showing the conversion of potassium tetrafluoroborate intopotassium chloride using a quaternary ammonium chloride ionic liquid.Equation 3 is an exemplary reaction showing the conversion of potassiumtetrafluoroborate into potassium chloride using a phosphonium chlorideionic liquid.KBF₄+R₄N⁺Cl⁻→KCl+R₄N⁺BF₄ ⁻ (R=Propyl, Butyl, Cetyl)  Eq. 2KBF₄+R₄P⁺Cl⁻→KCl+R₄P⁺BF₄ ⁻ (R=trihexyltetradecyl)  Eq. 3

In step 3440, the aqueous layer containing potassium chloride, rubidiumchloride, and/or cesium chloride, is isolated using appropriateseparation techniques. It will be apparent to one of skill in the artwhich separation techniques may be employed to isolate the aqueouslayer. For example, the aqueous layer containing potassium chloride isthen allowed to evaporate to dryness, resulting in solid potassiumchloride. In exemplary embodiments, the percentage conversion ofpotassium tetrafluoroborate to potassium chloride is between about 60 to90%. In some embodiments, the percentage conversion of potassiumtetrafluoroborate to potassium chloride is at least about 60%. In someembodiments, the percentage conversion of potassium tetrafluoroborate topotassium chloride is at least about 70%. In some embodiments, thepercentage conversion of potassium tetrafluoroborate to potassiumchloride is at least about 80%. In some embodiments, the percentageconversion of potassium tetrafluoroborate to potassium chloride is atleast about 90%. In further embodiments, the purity of the resultingpotassium chloride is at least 98%.

As a result of the removal of potassium, rubidium or cesium, acomposition is produced that has reduced concentrations of potassium,rubidium or cesium.

As shown in FIG. 10, in some embodiments, once the potassium, rubidium,or cesium has been removed from the brine, the brine is injected intothe ground 3450.

Preparation of Potassium Chloride, Rubidium Chloride, and/or CesiumChloride Using Ion Exchange Media

Referring now to FIG. 11, process 3500 details a method for thepreparation of potassium chloride from potassium tetrafluoroborate usingion-exchange media. Similar process can be employed for preparation ofrubidium chloride and/or cesium chloride from rubidium tetrafluoroborateand/or cesium tetrafluoroborate. Steps 3510 and 3520 are the same assteps 3410 and 3420 described above for FIG. 10. In step 3530, potassiumtetrafluoroborate is supplied to an ion-exchange media mixture. Theion-exchange media mixture can be prepared by mixing the ion-exchangemedia with water. In certain embodiments of the invention, the potassiumtetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate are prepared using the methods described herein. Insome embodiments, the ion-exchange media is selected from quaternaryammonium functional resin beads. One exemplary resin bead is theDOWEX-K-21 resin bead.

In an embodiment, potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate are added to theion-exchange media mixture in an amount between about 0.5 to 10 grams ofpotassium tetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate per 100 g of exchange media mixture. The ion-exchangemedia mixture with the potassium tetrafluoroborate, rubidiumtetrafluoroborate, and/or cesium tetrafluoroborate is then heated untilthe potassium tetrafluoroborate, rubidium tetrafluoroborate, and/orcesium tetrafluoroborate are dissolved. In some embodiments, the mixtureis heated to a temperature of between about 70 to 100° C., andalternatively to about 90° C. in some embodiments, the mixture is heatedto a temperature of between about 80 to 100° C. In some embodiments, themixture is heated to a temperature of about 70° C. In some embodiments,the mixture is heated to a temperature of about 75° C. In someembodiments, the mixture is heated to a temperature of about 80° C. Insome embodiments, the mixture is heated to a temperature of about 85° C.In some embodiments, the mixture is heated to a temperature of about 90°C. In some embodiments, the mixture is heated to a temperature of about95° C. In some embodiments, the mixture is heated to a temperature ofabout 100° C. In some embodiments, the mixture is also stirred duringthe heating step. In exemplary embodiments, the mixture is stirredvigorously intermittently for 30 seconds at two minute intervals.

After heating the ion-exchange media mixture to dissolve the potassiumtetrafluoroborate, rubidium tetrafluoroborate, and/or cesiumtetrafluoroborate, the mixture separates into an aqueous layer thatincludes potassium chloride, rubidium chloride, and/or cesium chlorideand a solid ion exchange media layer. In step 3540, the aqueous layercontaining potassium chloride, rubidium chloride, and/or cesium chlorideis isolated using appropriate separation techniques, which will beapparent to one of skill in the art. The aqueous layer is then dried,resulting in solid potassium chloride, rubidium chloride, and/or cesiumchloride. In exemplary embodiments of the invention, the percentageconversion of potassium tetrafluoroborate to potassium chloride isbetween about 60 to 90%. In some embodiments, the percentage conversionof potassium tetrafluoroborate to potassium chloride is at least about60%. In some embodiments, the percentage conversion of potassiumtetrafluoroborate to potassium chloride is at least about 70%. In someembodiments, the percentage conversion of potassium tetrafluoroborate topotassium chloride is at least about 80%. In some embodiments, thepercentage conversion of potassium tetrafluoroborate to potassiumchloride is at least about 90%.

As shown in FIG. 11, in some embodiments, once the potassium, rubidium,or cesium has been removed from the brine, the brine can be injectedinto the ground 3560.

Cesium can also be removed from brines using known methods, such asthrough the use of silicotitanate.

Brines that can be used in the various methods described herein caninclude any type of brine. In some embodiments, the brine is ageothermal brine. In further embodiments, the geothermal brine is aSalton Sea geothermal brine. In other embodiments, the brine is aconcentrated geothermal brine. The treated brines described herein canbe used for a variety of purposes. In some embodiments, the treatedbrines are used in a process to extract minerals remaining in the brine.In some embodiments, the treated geothermal brine is used in a methodwhereby the treated brine is injected into a geothermal reservoir.

In some embodiments, the compositions of the present invention haveimproved injectivity due to the reduction in concentration of silica,iron, potassium, rubidium, cesium, and/or other elements, as removal ofthese components of the brine reduce scaling in the well.

EXAMPLES Example 1 Selective Removal of Silica Using Aluminum Salts

A simulated brine was prepared to mimic the brine composition fromexemplary Salton Sea deep test wells (post reactor crystallizerclarifier system), having an approximate composition of 260 ppm (mg/kg)lithium, 63,000 ppm sodium, 20,100 ppm potassium, 33,000 ppm calcium,130 ppm strontium, 700 ppm zinc, 1700 ppm iron, 450 ppm boron, 54 ppmsulfate, 3 ppm fluoride, 450 ppm ammonium ion, 180 ppm barium, 160 ppmsilica (measured as silicon dioxide), and 181,000 ppm chloride. Thesilica was added to the brine as acidified sodium silicate solution,with the target of a concentration of about 160 ppm, the anticipatedvalue for the test well brine after undergoing a clarifying process topartially remove silica. The pH of the simulated brine was between about3 and 4, and was subsequently adjusted with sodium hydroxide or othersuitable base.

To enhance separation of the aluminosilicates from the brine onceprecipitated, aluminosilicates are recycled to contact them with a freshbatch of brine. Yjos enhances silica removal by increasing the size ofthe particles, making it easier to separate them physically. Theamorphous aluminosilicate material was prepared by neutralizing aconcentrated sodium silicate solution with an aluminum chloride salt.Specifically, 710 g of Na₂SiO₃.9H₂O was dissolved in 400 mL of distilledwater. To the solution, 420 g AlCl₃ was slowly added while stirring toproduce a wet paste of precipitated material. The paste was dried at 60°C. in an oven overnight and washed with Milli-Q water to remove fines toproduce a solid. The resulting solid was relatively insoluble (relativeto pure amorphous silica) and suitable for use as a seed material forsubsequent silica removal tests.

Approximately 1.6 mL of a 0.1M solution of AlCl₃ was added toapproximately 60 mL of the simulated brine solution, which had aninitial silica concentration of about 160 ppm and a pH of about 5.Approximately 1.5% by weight (relative to the total mass) of solidamorphous aluminosilicate was added to the solution. The AlCl₃ wasslowly added in an amount equal to the molar amount of silica solutionto achieve a ratio of silica to aluminum of about 1:1. The solution washeated to approximately 95° C. and stirred constantly. The pH wasmonitored and adjusted by titrating with sodium hydroxide or calciumhydroxide to maintain the starting pH of about 5. The solution wasallowed to stir for approximately 10 minutes, during which the silicaand aluminum reacted to selectively precipitate on the seed material,thereby removing both aluminum and silica from the solution. Themonomeric silica content (i.e., non-amorphous aluminosilicate content)dropped to approximately 25-40 ppm upon addition of base to maintain thepH at about 5. An additional 5-15% of the silica, present precipitatedover the next 30 minutes. Total silica removal for the process after 15minutes of stirring was about 95%, resulting in a brine solution havinga silica content of approximately about 10 ppm. The aluminumconcentration of the solution, after precipitation of the silica, wasbetween about 2-10 ppm.

Example 2 Selective Removal of Silica Using Iron

A simulated brine was prepared to mimic the brine composition of testwells found in the Salton Sea, having an approximate composition ofabout 252 ppm lithium, 61,900 ppm sodium, 20,400 ppm potassium, 33,300ppm calcium, 123 ppm strontium, 728 ppm zinc, 1620 ppm iron, 201 ppmboron, 322 ppm sulfate, 3 ppm fluoride, 201 ppm barium, 57 ppmmagnesium, 1880 ppm manganese, 136 ppm lead, 6 ppm copper, 11 ppmarsenic, 160 ppm silicon dioxide, and 181,000 ppm chloride. Thesimulated brine (1539.2 g) was sparged with air for about 60 minutes,during which time pH was measured. A calcium hydroxide slurry having 20%solids by weight was added dropwise after 60, 90, and 120 minutes (totalweight of the calcium hydroxide slurry added was 13.5 g; calciumhydroxide was 2.7 g dry basis) to the solution. The pH was monitoredthroughout the reaction and was initially allowed to fall, than adjustedto a pH of about 5 with the addition of calcium hydroxide after 60minutes, and maintained at about a pH of 5 thereafter. The reaction wasallowed to stir while the pH was maintained at about 5. Total reactiontime was about 180 minutes. A white precipitate was collected, washedand weighed, providing a yield of about 95% recovery of the silicapresent in the brine and about 100% of the iron present in the brine.

Example 3 Selective Removal of Silica Using Activated Alumina

A 50 mL brine solution having approximately 180 ppm dissolved silica waspassed through a 2.5 cm diameter column filled to a depth of 20 cm andcontaining approximately 0.5 g activated alumina and about 1.2 g water.The silica preferentially adsorbed onto the alumina and was removed fromthe solution. The activated alumina had a surface area of about 300 m²/gand a grain size of between about 8-14 mesh (˜2 mm diameter). The totalbed volume was about 102 mL. The temperature during the step ofcontacting the silica containing brine and the activated alumina wasmaintained between about 90 and 95° C.

The concentration of silica in the brine was monitored by measuringmonomeric silica using the molybdate colorimetric method and usingAtomic Absorption for total silica. Silica values were significantlylower in the exit solution due to adsorption of the silica on theactivated alumina. Saturation of the activated alumina, in the columnwas indicated by a sudden increase in silica concentration in the exitsolution. A total loading of about 1.8% by weight of silica (SiO₂) onthe activated alumina was achieved.

To regenerate the alumina, for another cycle of silica removal, thealumina was first washed with 5 bed volumes of dilute water in order toremove an salt solution remaining in the pores. This removed only asmall amount of silica from the alumina. The alumina was then reactedwith a dilute (0.1M) sodium hydroxide solution at a temperature ofbetween about 50-75° C. until a desired amount of silica has beenremoved. The alumina was then rinsed with between about 2-3 bed volumesof dilute acid to prepare the surface for the next silica adsorptioncycle.

Example 4 Continuous Processing of Geothermal Brine

To a brine solution comprising about 200 mg/L Li, 75,000 mg/L Na, 24,000mg/L K, 39,000 mg/L Ca, 156 mg/L Sr, 834 mg/L Zn, 539 mg/L B, 219 mg/LBa, 160 mg/L SiO₂, and 215,500 mg/L Cl and maintained at about 95° C.was added approximately 1.5% by weight aluminosilicate seed. Toapproximately 39 mL of the brine solution was added 1.07 mL of a 0.1Msolution of AlCl₃ such that the ratio of SiO₂:Al was 1:1. About 0.45 ME,of a 1N solution of NaOH was used to titrate the pH of the solution toabout 5. The solution was heated and stirred for about 10 minutes toensure complete precipitation of the aluminosilicate.

Analysis of both the feed and the output fluids during silica removalyielded mixed results. Comparing the results of molybdate bluecalorimetry (MBC; useful for quantifying monomeric silica) and ICP-OESyielded silica levels that were significantly lower than input levels(160 mg/L).

As shown in Table 1, the results of several methods for the removal ofsilica from a brine solution were tested. Both Ca(OH)₂ and NaOH wereinvestigated, as was NaOH along with a 10% excess of AlCl₃. For the useof an excess of AlCl₃, the additional AlCl₃ was added approximately 2minutes after initiation of the reaction, and additional NaOH wastitrated into the reaction mixture to maintain a pH of about 5. Finally,NaOH and polymerized aluminum in the form of aluminum chlorohydrate(PAC) was also investigated, instead of AlCl₃, and was prepared in situby titrating NaOH into AlCl₃ until a pH of about 4.5 was achieved.Additional base was added to raise the pH to about 5.

Both Ca(OH)₂ and NaOH were effective in both increasing the pH of thesolution, and in removing silica, with Ca(OH)₂ being slightly moreeffective at removing silica than NaOH, and removing at least about 80%of the silica present. Precipitation of silica by contacting with anexcess of AlCl₃ resulted in the precipitation of nearly 87% of silicapresent. Finally, use of the PAC resulted in the removal of about 84% ofthe silica present.

TABLE 1 Test Condition ICP MBC % SiO₂ % SiO₂ remaining % SiO₂ remaining% SiO₂ in solution removed in solution removed Ca(OH)₂ 17 83 19 81 NaOH28 72 20 80 NaOH + 110% AlCl₃ 16 84 13 87 NaOH + PAC 17 83 15 85

Example 5 Silica Removal Process Using Aluminum Salts

Approximately 60 mL of brine containing about 160 mg/L silica at a pH of5 was added to 1.07 g of amorphous aluminosilicate seed (˜1.5 wt. %solids). Approximately 1.6 mL of a 0.1M solution of aluminum chloride(AlCl₃) was added to the brine solution. The solution was stirred,maintained at nominally 95° C., and the pH monitored. The pH dropped toabout 2.7 upon addition of the AlCl₃ solution. Approximately 13 mL of asaturated and filtered Ca(OH)₂ solution was added. Silica and thealuminum salt formed precipitates, yielding a brine solution having asilica content of about 0.23 mg/mL.

Example 6 Packed Bed Testing

A hold-up vessel and packed bed tester (HUV-PB) were used in the packedbed testing. A baffled, plug-flow design with stirred sections to keepsolid particles suspended in solution was employed. The plug-flow designwith mixing is important as it maintains a constant and narrow residencetime distribution (RTD) while preventing premature deposition ofsuspended solids, which would bias scaling and packed-bed fouling rates.

The test set-up included brine pumping and metering equipment, a hold-upvessel (HUV) to provide controlled residence times similar to afull-scale injection system, and related controls and instrumentation.

A HUV sized for the minimum and maximum hold-up time for injectionpipelines and wellbores was used to test the fouling rate across thepacked bed. The fouling rate was monitored by real-time pressure drop(ΔP) signals at constant flow through the packed bed.

The packing configuration and flow through the packed bed was designedto provide accelerated fouling compared to that occurring in theinjection well. The packed beds were packed with screened drilling rockchips from a well hydrothermal zone. The rock chips were primarily oftwo types: 1) hydrothermally-crystallized fine-grained granitic materialcomposed of quartz and feldspar and 2) silica-bonded meta-siltstone. Therock chips were uniformly packed to allow for the measurement ofrelative fouling rates under process conditions for each test.

The run time of each experiment depended on the behavior of the brineacross the packed bed and the increase in pressure across the packedbed. If a pressure drop maximum was not reached, the test was run for upto 2 weeks before discontinuation of the test.

A side-stream of brine was supplied to the packed bed throughheat-traced packed bed tubing at about 10 psig from continuously flowingbypass loops. The brine streams were metered by positive-displacementperistaltic pumps at a controlled ratio through a HUV to simulate theaverage residence time in the injection pipeline and well casings. TheHUV was fitted with baffles and mixing paddles to provide plug flowwithout settling of suspended solids. The brine was then pumped underhigh-pressure (up to 1000 psig) through the columns packed with rockchips in order to simulate the reservoir formation.

During each test, data collection included brine flow rate, temperature,pressure, and differential pressure for each of the columns. Brinesamples were collected for chemical analysis upstream and downstream ofthe beds. The tests were run until the pressure drop (ΔP) across thepacked bed indicated significant plugging (approaching 1000 psig) whilethe brine flow rate through the column was maintained at a constant rateby a positive displacement pump. The tubes had injection brine pumpedthrough them until the pressure reached about 1000 psig at 1 LPM brineflow. The tests were concluded at 2 weeks, if the pressure drop of 1000psig was not experienced.

At the end of each test the packed bed and tubing test sections wereweighed to determine the amount of scale deposited and the residual bulkporosity of the packed bed was measured. Cross-sections of the packedbed were examined by Scanning Electron Microscopy (SEM) and X-raydiffraction (XRD). Brine samples and deposited solids in the tubing werealso analyzed for chemical composition.

The test runs were performed in accordance with Table 2.

TABLE 2 Test 1 Untreated Brine (UB) Test 2 Treated Brine (TB) Test 3 50%UB:50% TB Test 4 Untreated Brine (UB) Test 5 50% UB:50% TB Test 6Treated Brine (TB) Test 7 Untreated Brine (UB) Test 8 Treated Brine (TB)Test 9 50% UB:50% TB Test 10 Untreated Brine (UB)

Treated brine was brine that had been subjected to a silica managementand iron removal step as described in example 4 above (continuousremoval of silica). The brine was treated by first oxidizing the Fe(II)to Fe(III) and precipitating it as FeO(OH) with the addition of lime (asdescribed herein). The lithium was extracted using a granulated sorbentbased on a lithium aluminate intercalate. Untreated brine was brine thathad been flashed for purposes of extracting energy, but which had only aportion of silica removed, and had not been processed to remove iron, ina process in accordance with that described in U.S. Pat. No. 5,413,718.The untreated brine had approximately 160 mg/kg of silica. The 50:50blends were 50:50 by volumetric flow rate of treated and untreatedbrine.

Lithium Extraction Step

Lithium was extracted with a granular lithium aluminate sorbent placedin two five foot deep and 18 inch diameter columns that were run inalternating sequences of load and strip. Each operation wasapproximately two hours in duration. The sorbent was made according tothe process described in U.S. Pat. No. 8,574,519, which is herebyincorporated by reference in its entirety. Once the brine had passedthrough the columns it was recovered in a holding tank before a part ofthe flow was pumped packed bed test. The lithium was reduced fromapproximately 250 mg/kg to generally less than about 100 mg/kg andpreferably less than about 15 ppm.

The pressure profiles of each run are shown in FIGS. 12-20, and aresummarized in Table 3 below.

TABLE 3 Packed Bed Days of Operation (to 1000 psi stop-point) SourceAverage Untreated Brine 1.38 1.67 0.97 1.34 days (Test 1) (Test 4) (Test7) Treated Brine +15.0   4.59 +13.0   +10.9 days   (Test 2) (Test 6)(Test 8) 50:50 blend 1.39 3.28 4.60 3.09 days (Test 3) (Test 5) (Test 9)

Comparing the differential pressure profiles from FIGS. 12, 13, and 14against the differential pressure profiles from FIGS. 14, 15, and 16,the 50:50 brine blend run times were equal or better than the untreatedbrine, which shows that the blend is not likely to cause scalingproblems as quickly as untreated brine. The longest run times wereobserved with the treated brine as shown in FIGS. 18, 19, and 20, whichran long enough that two of the runs were terminated at two weeks. Themaximum potential run time for treated brine, Test 2, FIG. 18, is notknown, but an extrapolation of the trend shows it may have been as longas 6 weeks. The long run time of the treated brine is likely due to thelack of iron and silica in the brine solution. Thus, injection oftreated brine appears to give the best outcome for injectivity and longterm well permeability.

As shown in Table 4, the differences between the treated and untreatedbrines were the almost total removal of Fe, Si, and As, the significantreduction in Li, Ba, SO₄, F, and Pb concentrations, and the increase inpH, oxygen concentration, and ORP in the treated brine relative to theuntreated brine. Removal of Fe, Si, As, reduction in Pb concentration,increase in pH, oxygen, and ORP result from the silica managementprocess. Removal/reduction of Li is due to the lithium extractionprocess. Reduction in Ba, SO₄, and F concentrations was due to BaSO₄ andCaF₂ precipitation during the silica management process. Since Fe and Siare major scaling components, the ultimate impact of the brine treatmentprocess on brine chemistry will reduce the scaling potential of thedepleted brine and improve injectivity.

TABLE 4 Treated brine relative to untreated Analyte brine Temperature−15-20° C. pH +0.8 units ORP +300 to 500 mV Ca  −3% Fe −100%  Si −97% Li−90% As −100%  Pb −30%-50% Ba −60% SO₄ −55%

The chemistry of the brines were measured before and after residencetime in the packed bed and blending in the HUV, to ensure that no majorchemical reactions were taking place during the packed bed testing. Asignificant reaction would deplete the brine in one or more elements.

In FIGS. 21 through 25, the first column of each element shows the brinechemistry as it entered the HUV, the second column of each element showsthe brine chemistry as it exited the HUV, and the third column shows thebrine chemistry of a sample pulled 30 minutes from the post-HUV sample.The chemistry of Test 1 (untreated brine) was not measured, as itterminated sooner than expected, before chemical samples could be taken.However, Test 4 is a repeat of the same test and the results are shownin FIG. 21, and due to the consistency seen in the brines it is believedthat Test 1 would yield similar results.

As shown in FIGS. 22 and 23 for treated brines and in FIGS. 24 and 25for 50:50 blend brines, it was observed in almost every case that anychange in the pre- and post-HUV levels was small, and within the normalsample variation. The implication of this result is that the chemistryof the brine is stable during testing, and that there are no majorchemical reactions for precipitation reactions that effect brinechemistry in the packed bed. Even in the 50:50 blend brine (FIGS. 24 and25), there were no significant differences before and after the HUV. The50:50 blend brine does show more variability, likely due to a smallamount of Fe oxidation that also precipitates Si. Typical pH of thetested brines are shown in Table 5.

TABLE 5 Untreated Brine Treated Brine 50:50 Blend Average pH 4.61 5.675.20 Std. Dev. 0.23 0.27 0.09 Samples 20 34 9

To evaluate the scale, cut sections of the packed beds from Tests 1through 5 were submitted for petrologic (mineralogical) evaluation ofsolids precipitated or trapped during packed bed testing. Scanningelectron microscopy and X-ray diffraction analyses were conducted tocharacterize the chemical deposits and suspended solids that weretrapped in the rock matrix. A sample of the unexposed matrix materialwas also provided in order to compare the fine solids with the originalrock material.

Detailed SEM analyses of the scale and fine particles from the fivetests show a variety of textures and particle morphologies. Associatedspot elemental analyses reveal the composition of each type of finematerial. The dominant type of fine material consisted of darkgreen-colored, amorphous iron silicate with subtle variations based ontexture and elemental composition. FIGS. 26 through 31 show low and highmagnification SEM images from the testing of untreated, treated and50:50 blend brines.

FIGS. 26 and 27 show low and high magnification SEM images from thetesting of untreated brines. The untreated brine used in Tests 1 and 4,showed smooth, botryoidal (globular textured) particles composed ofrelatively pure iron silicate. More crumbly, rough-textured, or fuzzyaggregates were composed of iron silicate with minor calcium andaluminum. In places, more flaky or webby-textured surfaces were composedof iron silicate with potassium, aluminum, and calcium. This materialcould possibly represent a smectite-like clay.

FIGS. 28 and 29 show low and high magnification SEM images from thetesting of treated brines. The treated brine used in Test 2 formed afine, cracked crust composed of dehydrated iron oxyhydroxide withmanganese, chromium, and minor silica. In places, trace amounts ofnickel and zinc were also present in the Fe—Mn oxyhydroxide. The Fe—Mnoxyhydroxide formed a thin brown coating on the drill cuttings.

FIGS. 30 and 31 show low and high magnification STEM images from thetesting of 50:50 blend brines. The 50:50 blend brine used in Tests 3 and5 formed Fe and NaCl deposits in a fine solid form. These weresubmicron-sized crumbly deposits. The iron chloride had a consistentcomposition with minor calcium and potassium. Spot analyses alsoconsistently showed minor silica with the iron chloride and it wasdifficult to determine whether this was one compound (such aseltyubyuite) or an iron-calcium-potassium chloride admixed with opalinesilica. XRD analyses indicated minor amounts of opal-A in these twosamples. Based on how the chloride crystals in the sample wereintermixed with the other scale material, it was possible that thechlorides had precipitated out of solutions during mixing and reaction.This was likely due to the lower temperature of the treated brine whenit mixes with the untreated brine. In a real injectivity situation, thetemperatures of injectivity will be higher and this will keep thechlorides in solution.

A material of interest from the packed bed tests was the small scaleparticles and chemical deposits attached to the rock chip matrix. If thetotal rock sample was used, the rock matrix would dilute the scaleminerals in the sample, rendering them too dilute to be identifiable inthe XRD scans. Therefore, the small-scale particles were washed from thematrix rock and concentrated to more accurately measure the mineralogyand composition of the scale.

A summary of the separated packed bed tube scale is shown in Table 6.Other than halite (Nag) precipitated in the 50:50 blend in Tests 3 and5, all of the major crystalline material in the XRD patterns wasattributed to minerals from the rock fragments in the drill cuttings.Other than trace to minor amounts of crystalline iron oxides (magnetite,maghemite) and iron oxyhydroxides (goethite, akaganeite), most of thechemical deposits appeared to be amorphous or too poorly crystalline todiffract the X-rays.

TABLE 6 XRD Mineralogy Relative Wt % Salton Sea Drill Test Test TestTest Test SAMPLE ID Cuttings #1 #2 #3 #4 #5 Quartz 63 31 41 0 7 17Plagioclase 15 14 11 1 0 8 K-Feldspar 5 5 8 2 1 3 Calcite 2 2 0 0 0 1Dolomite 1 0 0 0 0 0 Ankerite 1 0 0 0 0 0 Epidote 5 11 7 30 2 6 Barite 00 1 0 0 0 Pyrite 0 0 0 0 0 0 Magnetite 0 1 6 1 4 2 Maghemite 0 2 0 0 3 1Geothite 0 0 0 0 3 0 Akaganeite 0 0 1 0 0 3 Halite 0 0 0 38 0 14 Total(Non-Clay) 91 66 74 71 20 55 Illite + Mica 0 0 4 9 12 11 Mixed-LayerIllite- 0 0 0 0 0 0 Smectite Chlorite 8 11 22 1 4 18 Total (Clay) 9 1127 10 16 29 Total (Crystalline 100 76 100 81 36 84 Material) Amorphous(Opal-A) 0 24 0 19 64 16 GRAND TOTAL 100 100 100 100 100 100(Crystalline and Opal-A)

A summary of the clay fines from the packed tube scale is shown in Table7. The dominant clay material was fine mica, which was likely acomponent of the drill cuttings matrix.

TABLE 7 Clay XRD Mineralogy (<4 micron size fraction, Relative Wt %)Rock Test Test Test Test Test SAMPLE ID chips #1 #2 #3 #4 #5 %Expandability of I/S clay 25 0 35 10 0 0 (smectite interlayers) Mica 2667 31 35 71 44 Mixed-Layer Illite-Smectite 13 0 23 39 0 0 (I/S)Kaolinite 0 0 0 0 0 18 Chlorite 61 33 46 26 29 38 TOTAL 100 100 100 100100 100

Total suspended solids is also an important parameter of the brinecompatibility testing. The treated brine had lower TSS values than theuntreated brine, and even the 50:50 blend brines had less than or equalTSS to the untreated brine.

The TSS of the untreated brine was measured using an accurate in-linemethod throughout the series for tests. Those values are shown in FIG.32. The data showed that the TSS of the untreated brine average wasabout 20 ppm, but it was variable, and sometimes reached 50 ppm.

The TSS were also measured on the brines used for packed bed testing,before and after the HUV using a vacuum filtration method. The valuesare shown in FIG. 33. As expected, the treated brines possessed a lowTSS due to the lack of scaling components and filtration duringprocessing. The untreated brine and the 50:50 blend brine showed higherTSS, at a similar range of values.

Shown in FIGS. 34 and 35 are the results of the treated brine (Tests 2,6, and 8), untreated brine (Tests 1, 4, and 7), and 50:50 brine blends(Tests 3 and 5) analysis for percent weight gain and residual bulkporosity.

The 50:50 blend brines performed equal to or better than the untreatedbrine in packed bed simulated well testing. This suggests that there areno major compatibility or reaction issues, and that reservoirpermeability would not be any worse than the untreated brine.

In addition, treated brine performed far better on the packed bedpermeability testing than any other brine or brine blend tested. This islikely due to the lack of scaling compounds in the treated brine, alongwith a lower TSS value. The results suggests that an injection fluid of100% treated brine will have the best injectivity and permeabilityperformance than any other brine tested.

One improvement that can be made to the 50:50 blend brine, that may makeit perform even better, is to provide dilution water or maintain hightemperature to prevent halite (NaCl) from coming out of solution beforeinjection.

Example 7 Preparation of Treated Geothermal Brine Compositions withReduced Concentrations of Iron and Silica

In another example, four 20 L plastic pails of geothermal brine from theSalton Sea, Calif. that were subjected to silica processing, weretransferred to the reactor. The combined sample was agitated at 80° C.for 4 hours and then samples were collected for an elemental analysis.Table 8 shows concentrations of various elements in samples of thegeothermal brine samples.

TABLE 8 Element Concentration in Sample 1 Concentration in Sample 2analyzed mg/L mg/L Arsenic <3 <3 Barium 42 44 Iron 1900 1900 Lithium 310309 Lead 130 130 Silicon 30 30A laboratory scale stage 1 precipitation was conducted on a sample ofthe adjusted geothermal brine. The brine was sparged with air for 20minutes, and then approximately 70% of the required lime was added tothe reaction solution. The balance of the lime was added over the next20 minute period. The reaction was conducted for a total time of 150minutes. During the reaction period, kinetic samples were collected atset reaction times. At the end of the reaction period the slurry wasprocessed in the standard manner. The Oxidation Reduction Potential ofthe solution after 20 minutes of air sparging was 200 mV. The solutionpH value was 3.0. The solution concentrations for iron and silica wereplotted against elapsed reaction time in FIG. 34. Approximately 98% ofthe silica precipitated and the final silica concentration was reducedto 6 mg/L after 65 minutes. The iron was removed by about 65% of the Feprecipitated and the final Fe solution concentration was 940 mg/L.

Example 8 Preparation of Larger Scale Treated Geothermal BrineCompositions with Reduced Concentrations of Iron and Silica

In another example, about 69 liters of adjusted geothermal brine wassubjected to processing on a larger scale. An insulated double walledpolypropylene reactor (˜80 L) was equipped with a polycarbonate lid thathad multiple access ports for the various pieces of equipment andinstrumentation. The overall reaction as observed at about 81° C.,following initial sparging time of 40 minutes with an airflow of 2.25L/min. About 84 g of dry lime was added. The Si and Fe solutionconcentrations are plotted against reaction time in FIG. 35. Some of theinitial and final test conditions for the bulk test are summarized inTable 9.

TABLE 9 Condition Initial Reading Final Reading pH 4.43 5.33 ORP, mV −14−293

Analysis of the data from this experiment revealed that there wasinsufficient mixing of the solution that resulted in poor suspensions ofthe initial contained solids. As the reaction progressed, the majorityof these solids dissolved and released iron and silica to solution. Thesilica concentration was reduced to below 10 mg/L and iron was removedto about 900 mg/L. Changes in the air sparging period or changes in theair flow to the system were made to increase the iron removal. Thefiltrate from the reactor was subjected to further processing at atemperature of about 95° C. Air was sparged into the system for about 20minutes and then lime was added and the pH constantly monitored. Airsparging continued. The iron concentration at pH 6.0 was below 50 mg/Land, therefore, the reaction was stopped and the reaction slurry wasprocessed. The Si and Fe solution concentrations were plotted againstreaction time in FIG. 36. These experiments revealed that by changingthe conditions of the treatment, one could achieve the desired levels ofiron and silica removal from the geothermal brine.

Example 9 Preparation of Treated Geothermal Brine Compositions withReduced Concentrations of Iron and Silica from Brine Treatment at aPhysical Plant

Producing treated brines with reduced silica and iron concentrationminimizes the problems downstream during extraction of minerals likezinc and lithium from the treated brine. As discussed herein, therestating brines with reduced silica and iron concentration is much lesslikely to damage the injection wells, because all major scale-producingelements have been removed.

The methods and systems described herein were deployed for silicamanagement of geothermal brine at two different physical plants. Onephysical plant included three rectangular continuously stirred tankreactors for iron (II) oxidation and iron (III) oxyhydroxideprecipitation, and an inclined plate (lamella) clarifier for initialsolid/liquid separation. Another physical plant included two cylindricalcontinuously stirred tank reactors and a cylindrical conventionalrake-style clarifier. The second plant also implemented an improvedair-sparging/agitation system for more efficient iron (H) oxidation.Because of the decrease in number of reactors, and the increasedsparging efficiency, the total residence time in the reactor train couldbe reduced by a factor of 3. The switch to a conventional clarifier wasmade in part to minimize manual operations related to cleaning theclarifier lamella of sticky solids, and partly to provide data for aclarifier design that was suitable for scale up to commercial size.

Operations using the three-reactor physical plant included feeding brinefrom a geothermal energy producer at a specified rate between 3-6 gpm.Operational set points (pH, sparge rate, agitation) for the threereactors were adjusted following the experimental observation from pilotstudies. Flocculant was added initially to the clarifier based on batchflocculation tests, and adjusted as necessary to gain control of TSS inoverflow. The proportion of underflow directed to recycle, and therecycle return point(s) were set as desired for the specific pilotcampaign. Underflow advance was directed to the filter feed tank (orthickener), and then to pressure filter. Filtrate and thickener overflowwere generally recycled back to the first reactor. Filter cake wasperiodically removed from the pressure filter and directed to waste.

Operations using the two-reactor physical plant were essentiallysimilar. Table 10 shows a comparison of the sample operating conditionsat the two plants.

TABLE 10 Residence time at nominal Plant 5 gpm, min Feed/inlet/outletAgitation Sparging Clarifier Recycle 3-reactor 120 Inlet feed was pumpcontrolled; Variable speed; Sparging via Inclined plate Recycle plantadvance flow via gravity. single impeller perforated with integralunderflow Horizontal input near tank square U-tube flash tank and to R-1and R-2 bottom below agitator blade. at bottom of floc chambersHorizontal output near tank top. tank 2-reactor 40 or 20 Inlet feed ispump controlled; Variable speed; Sparging via Cylindrical Recycle plantdepending on advance flow via gravity. dual impeller; air injection withrake and underflow position of Vertical input at tank lower was intobrine separate floc to R-1 only outflow bottom; mixed with sparge air.8″ Rushton blade; feeds at tank mixing tank Two side outlet ports; upperupper was bottom yields 40 minute residence 8″ pitched blade time; loweryields 20 minute residence time at 5 gpm.

Previous studies indicate that at ˜110° C. the concentration ofdissolved silica in Salton Sea geothermal brine coming out of acrystallizer clarifier is ˜116 ppm. The feed brine composition varieddepending on variations in the geothermal brine and in the operations ofthe geothermal energy producer. For example without limitations, thevariations could arise from changes in dilution water added to thebrine, or from operations related to their flashing and subsequentprocessing.

In an exemplary set-up, similar to that shown in FIG. 6, geothermalbrine was subjected to a continuous process for the management ofsilica. Silica management system 1106 was carried out using two stirredvessels 1108 and 1110 provided in series. To first reactor 1108 ageothermal brine was supplied via line 1104 having an iron content ofapproximately 1500 ppm and a silica, content of about 160 ppm. The brineis added at a rate of about 6 gpm. Approximately 30 cfm of air wassupplied via line 1140 to each reactors 1108 and 1110, and was spargedthrough the geothermal brine. The operating temperature wasapproximately about 90 to 95° C. in reactor 1 and 85 to 90° C. inreactor 2.

After the addition of the air via line 1140′ to first reactor 1108, thepH dropped and was around approximately about pH 4.8 to 5.4. Air wasadded to second reactor 1110 via line 1140″ at a rate of about 30 cfmand a charge of approximately 10-25% by weight of an aqueous calciumoxide slurry at a rate of about 0.5 lb/min., which raised the pH in thesecond reactor to between about 5.0 and 5.6. The addition of the limeslurry initiated the precipitation of iron (III) hydroxide and ironsilicate. The geothermal brine, which included precipitates of iron(III) hydroxide or iron oxyhydroxide and iron silicate, was thensupplied from the second vessel 1110 to clarifier 1146 via line 1144. Anaqueous flocculant solution of Magnafloc 351, in a concentration betweenabout 0.005% and 1% by weight, such as about 0.025% by weight, wasprepared by supplying solid flocculent 1124 via line 1126 to flocculanttank 1128, where the solid was contacted with water 1120 supplied vialine 1122. The aqueous flocculant solution was supplied to clarifiervessel 1146 via line 1138 at a rate of about 0.01 gpm.

Two streams were produced from clarifier 1146. First clarifier productstream 1148 included the geothermal brine having a reduced concentrationof silica and iron, and was supplied to a secondary process, such aslithium recovery. Second clarifier product stream 1150 included solidsilica-iron waste, as well as some geothermal brine. The brine wassampled between reactors 1108 (Reactor 1) and after 1110 (Reactor 2)before as well as after the clarifier 1146 (clarifier overflow).

Table 11 shows the concentration of iron and silica after silicamanagement through the first reactor and after the second reactor in aphysical plant. Based on analysis of the data collected, the ironconcentration ranged from about 200 mg/L to 1000 mg/L, while the siliconconcentration ranged from about 1 to 60 mg/L.

TABLE 11 Fe concentrations (mg/kg) Si concentrations (mg/kg) FromReactor 1 Min 168 1 Max 828 43 Mode 307 10 Median 335 13 From Reactor 2Min 180 <1 Max 833 48 Mode 297 12 Median 261 14

Samples were analyzed from the feed brine and from the clarifieroverflow to determine the concentrations of silica and silicon. FIGS.37A and 37B show the histograms of silicon (not SiO₂) concentrations infeed brine (FIG. 37A) and clarifier overflow (FIG. 37B). While theconcentration of silicon in the feed brine ranged from 16-117 ppm, themean and median silicon concentrations were both about 55 ppm. While theconcentration of silicon in the treated brine from the clarifier rangedfrom 0-25 ppm, the mean and median silicon concentrations were bothabout 4 ppm. The SiO₂ concentration in the feed brine ranged from 32 to250 ppm, with a mean and median of 118 ppm. The silica in the clarifieroverflow ranged from 0.4 to 53 ppm, with a mean and median of 8.6 and7.7 ppm, respectively. Hence, ˜93% of the feed SiO₂ was removed by thesilica management circuit.

Samples were analyzed from the feed brine and from the clarifieroverflow to determine the concentrations of iron. The histograms inFIGS. 39A and 39B illustrate the iron concentrations in feed brine (FIG.39A) and clarifier overflow (FIG. 39B). While the concentration of ironin the feed brine ranged from 638-3830 ppm, the mean and median ironconcentrations were both about 1600 ppm. While the concentration of ironin the treated brine from the clarifier ranged from 0-636 ppm, the meanand median iron concentrations were about 20 ppm and less than 1 ppmrespectively.

Samples were also analyzed from another exemplary demonstration of theprocess. FIGS. 38A and 39B show histograms of dissolved silicon (notsilica) concentrations in feed brine (FIG. 38A) and clarifier overflow(FIG. 38B). While the concentration of silicon in the feed brine rangedfrom 27-98 ppm, the mean and median silicon concentrations were bothabout 53-54 ppm. While the concentration of silicon in the treated brinefrom the clarifier ranged from 1-25 ppm, the mean and median siliconconcentrations were both about 4 ppm. The range in feed SiO₂ was 58 ppmto 131 ppm with mean and median of 113 ppm and 115 ppm, respectively.SiO₂ in the clarifier overflow ranged between 2 and 53 ppm, with a meanand median of 8.9 and 7.8 ppm, respectively. There was similar removalefficiency in the 95% range. Samples were analyzed from the feed brineand from the clarifier overflow to determine the concentrations of iron.The histograms in FIG. 40 illustrate the iron concentrations in feedbrine (FIG. 40A) and clarifier overflow (FIG. 40B). While theconcentration of iron in the feed brine ranged from 980-3830 ppm, themean and median iron concentrations were both about 1670 ppm. While theconcentration of iron in the treated brine from the clarifier rangedfrom 0-258 ppm, the mean and median iron concentrations were about 18ppm and 3 ppm, respectively.

In another exemplary demonstration of the process, the treated brinewith reduced silica and iron concentration was fed to a lithium removalprocess, and the presence of arsenic, barium, iron, lithium, lead, andsilicon was analyzed at different stages of the operation, and theresults are shown in Table 12. Concentrations of calcium in thesetreated compositions can vary from about 30,000 ppm to about 46,000 ppm,with a median concentration of about 36,000 ppm. Concentrations ofsodium in these treated compositions can vary from about 40,000 ppm toabout 80,000 ppm, with a median concentration of about 61,150 ppm.

TABLE 12 Arsenic Barium Iron Lithium Lead Silicon Potassium ManganeseZinc Sampling ppm ppm ppm ppm ppm ppm ppm ppm ppm Silica Min 8 0 990 14449 27 10,990 889 288 Management Max 30 244 2085 387 110 61 25,990 1558540 Inlet Median 13 198 1673 248 92 54 17,920 1349 472 Silica Min 0 51 0122 43 1 9,063 695 208 Management Max 3 516 258 354 90 25 24,350 1556552 Outlet Median 0 154 3 251 78 4 18,480 1366 476 Brine Outlet Min 0 520 16 41 0 16,860 953 434 from Max <1 191 72 287 86 4 29,325 1803 614Lithium Median <1 120 1 45 65 3 21,020 1483 515 Extraction Column 1Brine Outlet Min 0 0 0 5 26 0 10,640 753 309 from Max 1 348 331 341 9212 33,850 2111 678 Lithium Median <1 108 1 46 73 3 19,920 1427 499Extraction Column 2

Example 10 Selective Removal of Potassium Using AmmoniumTetrafluoroborate

Approximately 100 grams of geothermal brine was heated to about 90° C.in a water bath. Approximately 3.5 grams of ammonium tetrafluoroboratewas added to the brine. White potassium tetrafluoroborate precipitateformed almost immediately. The mixture was vigorously shaken for 30seconds and then transferred to centrifuge tubes and centrifuged at 4000rpm for 4 minutes. Two layers formed, a clear aqueous layer and a whitepotassium tetrafluoroborate precipitate layer. The clear aqueous layerwas decanted off and the potassium tetrafluoroborate precipitate waswashed with deionized water at room temperature. The potassiumtetrafluoroborate precipitate yield was 2.4 grams.

Example 11 Selective Removal of Potassium Using Fluoroboric Acid

Approximately 100 grams of geothermal brine was heated to about 90° C.in a water bath. Approximately 5.0 grams of fluoroboric acid (as 48% byweight solution) was added to the brine. A white potassiumtetrafluoroborate precipitate formed almost immediately. The mixture wasvigorously shaken for 30 seconds and then centrifuged at 4000 rpm forfour minutes. Two layers were formed, a clear aqueous layer and a solidwhite potassium tetrafluoroborate precipitate layer. The clear aqueouslayer was decanted off and the potassium tetrafluoroborate precipitatelayer was washed with deionized water. The potassium tetrafluoroborateprecipitate yield was 2.65 grams.

Example 12 Selective Removal of Potassium Using Modified DOWEX-K-21Resin Beads

Approximately 100 grams of water was added to 40 grams of Dowex-K-21 ionexchange resin beads containing chloride ions. To this, 8 grams ofpotassium tetrafluoroborate was added and the resulting solution washeated to about 90° C. in a water bath for approximately 30 minutes. Thesolution was stirred occasionally during heating. All potassiumtetrafluoroborate dissolved in the first 5 minutes of the reaction. Theclear solution was decanted of and the tetrafluoroborate terminatedDowex-K-21 resin beads (modified resin beads) were separated from theclear solution. Approximately 50 grams of geothermal brine was heated toabout 90° C. in a water bath. Approximately 40 grams of the modifiedresin beads were added to the brine. The mixture was vigorously shakenfor 1 minute and then continued heating at 90° C. in a water bath. Awhite potassium tetrafluoroborate precipitate formed within 5 minutes.Heating continued for 5 more minutes. The liquid with the precipitatewas collected in a centrifuge tube. The liquid with the precipitate wasthen centrifuged at 4000 rpm for 4 minutes. The potassiumtetrafluoroborate precipitate yield was 0.4 grams.

Example 13 Potassium Chloride Conversion using TetrabutylammoniumChloride

Approximately 0.55 grams of tetrabutylammonium chloride (TBAC) wasdissolved in about 10 mL of water in a test tube and heated to about 85°C. Potassium tetrafluoroborate (approximately 0.25 grams), preparedusing the methods described above, was added to the solution and heatedwith occasional stirring until completely dissolved. A lighter whiteprecipitate formed and floated to the surface of the solution. Afterfive minutes, the white precipitate was separated from the aqueous layerof the solution. The aqueous layer was allowed to evaporate to dryness,producing solid potassium chloride. The reaction yielded 90 mg ofpotassium chloride.

Example 14 Potassium Chloride Conversion Using TrihexyltetradecylPhosphonium Chloride

Approximately 1.03 grams of trihexyltetradecyl phosphonium chloride wasadded to about 5 grams of water and heated to about 90° C. Approximately1.02 grams of potassium tetrafluoroborate, prepared using the methodsdescribed above, was added to the solution and stirred vigorously forabout 30 minutes. Two layers were formed, an aqueous layer and anorganic layer. The two layers were separated and the aqueous layer wasallowed to evaporate to dryness, producing solid potassium chloride. Thereaction yielded 0.5 grams of potassium chloride.

Example 15 Potassium Chloride Conversion Using DOWEX-K-21 Resin Beads

Approximately 8 grams of DOWEX-K-21 resin beads were added to 100 gramsof water and heated to 90° C. 1.0 gram of potassium tetrafluoroboratewas added to the solution and the solution was shaken vigorously for 30seconds every two minutes, for approximately 10 minutes. All of thepotassium tetrafluoroborate was dissolved in solution after 10 minutes.The resulting aqueous layer was separated from the resin beads andallowed to evaporate to dryness, producing solid potassium chloride.This reaction yielded 0.58 grams of potassium chloride.

Example 16 Potassium Chloride Conversion Using TrihexyltetradecylPhosphonium Chloride

Approximately 4.1 grams of potassium tetrafluoroborate was added to 7.3grams of water. To this suspension was added approximately 16.8 grams oftrihexyltetradecyl phosphonium chloride. The resulting mixture wasvigorously agitated at 90° C. for 2 to 10 minutes. The resulting mixturewas separated using a separatory funnel. The potassium chlorideconcentration in the final solution was approximately 23 wt. %. X-raypowder diffraction confirmed the presence of potassium chloride.

Example 17 Selective Removal of Potassium and Rubidium from a ReducedSilica Feed Using Fluoroboric Acid

A geothermal brine that had been subjected to a silica managementprocess and had reduced silica content was heated to about 90° C. in awater bath. Fluoroboric acid (as 48% by weight solution) was added tothe reduced silica geothermal brine, as shown in Table 13. A whitepotassium tetrafluoroborate precipitate formed almost immediately. Themixtures were vigorously shaken for 30 seconds and then centrifuged at4000 rpm for four minutes. Two layers were formed; a clear aqueous layerand a solid white potassium tetrafluoroborate precipitate layer. Theclear aqueous layer was decanted off and the potassium tetrafluoroborateprecipitate layer was washed with deionized water. The clear aqueouslayer was analyzed using ICP-OES. The results are shown in Table 14.

TABLE 13 Sample g XBF4/kg Brine brine wt. (g) brine, mL HBF4 wt. (g) 1 010 8.33 0 2 0.96 10 8.33 0.02 3 4.8 10 8.33 0.1 4 12 10 8.33 0.25 5 2410 8.33 0.5 6 36 10 8.33 0.75 7 48 10 8.33 1 8 60 10 8.33 1.25 9 72 108.33 1.5

TABLE 14 Fe K Li Mn Pb Rb Si Zn (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/Sample kg) kg) kg) kg) kg) kg) kg) kg) 1 0.2  19667 256 1417 93 287 4531 2 N.D. 18167 249 1433 89 280 4 537 3 N.D. 17000 247 1400 89 264 5520 4 N.D. 13917 248 1392 90 234 5 529 5 0.17 8417 23 1283 85 179 5 4896 N.D. 3500 249 1425 83 123 6 537 7 N.D. 925 235 1358 72 55 6 507 8 0.18392 251 1425 76 37 9 524 9 0.13 362 266 1508 74 32 11 565 N.D. indicatesthat the levels were below detectable limits.

Example 18 Selective Removal of Potassium and Rubidium from a ReducedSilica Feed Using Fluoroboric Acid

A geothermal brine that had been subjected to a silica managementprocess and had reduced silica content was heated to about 90° C. in awater bath. Fluoroboric acid (as 48% by weight solution) was added tothe reduced silica geothermal brine, as shown in Table 15. A whitepotassium tetrafluoroborate precipitate formed almost immediately. Themixtures were vigorously shaken for 30 seconds and then centrifuged at4000 rpm for four minutes. Two layers were formed; a clear aqueous layerand a solid white potassium tetrafluoroborate precipitate layer. Theclear aqueous layer was decanted off and the potassium tetrafluoroborateprecipitate layer was washed with deionized water. The clear aqueouslayer was analyzed using ICP-OES. The results are shown in Table 16.

TABLE 15 g XBF4/Kg Brine brine wt. (g) brine, mg/Kg HBF4 wt. (g) 1 0 5041.7 0 2 2.16 50 41.7 0.23 3 5.57 50 41.7 0.58 4 8.06 50 41.7 0.84 512.96 20 41.7 0.54 6 17.52 20 41.7 0.73 7 22.56 20 41.7 0.94 8 25.44 2041.7 1.06

TABLE 16 Fe K Li Mn Pb Rb Si Zn (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/Sample kg) kg) kg) kg) kg) kg) kg) kg) 1 <MQL 21917 131 <MQL <MQL <MQL1.31 1.31 2 <MQL 19000 121 0.93 <MQL <MQL 2.01 2.01 3 <MQL 17958 1250.44 <MQL <MQL 1.38 1.38 4 <MQL 16792 130 0.62 <MQL <MQL 1.30 1.30 5<MQL 14292 134 1.64 <MQL <MQL 1.33 1.33 6 <MQL 11125 121 0.62 <MQL <MQL1.23 1.23 7 <MQL 9208 127 0.48 <MQL <MQL 1.30 1.30 8 <MQL 7017 115 <MQL<MQL <MQL 1.23 1.23 <MQL or less than Method Quantification Limitindicates that the levels were below detectable limits of the method.

Example 19 Selective Removal of Potassium and Rubidium from a ReducedSilica Brine Using Ammonium Tetrafluoroborate

A geothermal brine that had been subjected to a silica managementprocess and had reduced silica content was heated to about 90° C. in awater bath. Ammonium tetrafluoroborate was added to the reduced silicageothermal brine, as shown in Table 17. A white potassiumtetrafluoroborate precipitate formed almost immediately. The mixtureswere vigorously shaken for 30 seconds and then centrifuged at 4000 rpmfor four minutes. Two layers were formed; a clear aqueous layer and asolid white potassium tetrafluoroborate precipitate layer. The clearaqueous layer was decanted off and the potassium tetrafluoroborateprecipitate layer was washed with deionized water. The clear aqueouslayer was analyzed using ICP-OES. The results are shown in Table 18.

TABLE 17 Sample g XBF4/Kg Brine Brine wt. (g) Brine, mL NH4BF4 wt. (g) 10 10 8.33 0 2 0.48 10 8.33 0.01 3 2.4 10 8.33 0.05 4 4.8 10 8.33 0.1 512 10 8.33 0.25 6 24 10 8.33 0.5 7 38.4 10 8.33 0.8

TABLE 18 Fe K Li Mn Pb Rb Si Zn (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/Sample kg) kg) kg) kg) kg) kg) kg) kg) 1 <MQL 19417 235 1883 83 191 2.6507 2 <MQL 18083 220 1817 78 183 2.6 465 3 <MQL 18167 224 1833 79 1812.8 473 4 <MQL 17583 220 1800 78 178 2.9 469 5 <MQL 16083 230 1892 83173 3.1 499 6 <MQL 9917 260 2017 93 135 3.8 531 7 <MQL 1542 218 1783 7942 7.8 455 <MQL or less than Method Quantification Limit indicates thatthe levels were below detectable limits of the method.

Example 20 Selective Removal of Potassium and Rubidium from a ReducedSilica Brine Using Calcium Tetrafluoroborate

Reduced silica brine was heated to about 90° C. in a water bath. Calciumtetrafluoroborate was added to the reduced silica brine, as shown inTable 19. A white potassium tetrafluoroborate precipitate formed almostimmediately. The mixtures were vigorously shaken for 30 seconds and thencentrifuged at 4000 rpm for four minutes. Two layers were formed; aclear aqueous layer and a solid white potassium tetrafluoroborateprecipitate layer. The clear aqueous layer was decanted off and thepotassium tetrafluoroborate precipitate layer was washed with deionizedwater. The clear aqueous layer was analyzed using ICP-OES. The resultsare shown in Table 20.

TABLE 19 g XBF4/Kg brine wt. brine, L Ca(BF4)2 Sample Brine (g) (brinedensity 1.2 g/cc) wt. (g) 1 0 10 8.33 0 2 2 10 8.33 0.02 3 10 10 8.330.1 4 25 10 8.33 0.25 5 50 10 8.33 0.5 6 75 10 8.33 0.75 7 100 10 8.33 1

TABLE 20 Fe K Li Mn Pb Rb Si Zn (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/ (mg/Sample kg) kg) kg) kg) kg) kg) kg) kg) 1 <MQL 14833 109 0.1 15 242 10.70.91 2 <MQL 14833 106 0.1 16 239 2.7 0.96 3 <MQL 14292 107 0.1 16 2294.4 0.95 4 <MQL 12208 106 0.1 16 209 1.6 0.99 5 <MQL 10292 111 0.2 16113 0.8 1.14 6 <MQL 5688 110 0.2 16 142 1.0 1.20 7 <MQL 2483 111 0.3 1699 1.1 1.34

Example 21 Selective Removal of Cesium from a Reduced Silica Brine UsingCrystalline Silicotitanate

A reduced silica brine was heated to about 90° C. in a water bath. Onegram of crystalline silicotitanate was added to 100 grams of reducedsilica brine and allowed contact for 3 hours, at pH 3, 5, and 8. Thecrystalline silicotitanate uptake of cesium was measured. Uptakeefficiency at pH 8 was 35.11%, at pH 5 was 77.46%, and pH 3 was 73.53%.The concentration of Cs was measured using atomic absorptionspectroscopy. The uptake efficiency is measured by analyzing the initialconcentration in the brine solution prior to contact with the CSTsorption media and again after contact.

As is understood in the art, not all equipment or apparatuses are shownin the figures. For example, one of skill in the art would recognizethat various holding tanks and/or pumps may be employed in the presentmethod.

The singular forms “a,” “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstances may or may not occur. The description includesinstances where the event or circumstance occurs and instances where itdoes not occur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art to which the inventionpertains, except when these reference contradict the statements madeherein.

As used herein, recitation of the term about and approximately withrespect to a range of values should be interpreted to include both theupper and tower end of the recited range.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

We claim:
 1. A treated geothermal brine composition, the compositioncomprising a treated geothermal brine having a concentration of silicaranging from about 0 mg/kg to about 15 mg/kg, a concentration of ironranging from about 0 mg/kg to about 10 mg/kg, and a concentration ofpotassium less than about 500 mg/kg, and comprising recoverable amountsof one or more metals selected from the group consisting of lithium,rubidium, and cesium or mixtures thereof.
 2. The treated geothermalbrine composition of claim 1, wherein the concentration of silica isless than about 10 mg/kg, the concentration of iron is less than about10 mg/kg, and the concentration of potassium is less than about 4000mg/kg.
 3. The treated geothermal brine composition of claim 1, whereinthe concentration of silica is less than about 15 mg/kg, theconcentration of iron is less than about 10 mg/kg, and the concentrationof potassium is less than about 4000 mg/kg.
 4. The treated geothermalbrine composition of claim 1, wherein the concentration of silica isless than about 10 mg/kg, the concentration of iron is less than about10 mg/kg, and the concentration of potassium is less than about 2000mg/kg.
 5. The treated geothermal brine composition of claim 1, whereinthe concentration of silica is less than about 10 mg/kg, theconcentration of iron is less than about 10 mg/kg, and the concentrationof potassium is less than about 1000 mg/kg.
 6. The treated geothermalbrine composition of claim 1, wherein the concentration of silica isless than about 5 mg/kg, the concentration of iron is less than about 10mg/kg, and the concentration of potassium is less than about 1000 mg/kg.7. The treated geothermal brine composition of claim 1, wherein theconcentration of silica is less than about 10 mg/kg, the concentrationof iron is less than about 10 mg/kg, and the concentration of potassiumis less than about 500 mg/kg.
 8. The treated geothermal brinecomposition of claim 1, wherein the concentration of silica is less thanabout 5 mg/kg, the concentration of iron is less than about 10 mg/kg,and the concentration of potassium is less than about 500 mg/kg.
 9. Thetreated geothermal brine composition of claim 1, further wherein thetreated geothermal brine has a concentration of rubidium ranging fromabout 30 mg/kg to about 200 mg/kg.
 10. The treated geothermal brinecomposition of claim 1, further wherein the treated geothermal brine hasa concentration of rubidium less than about 150 mg/kg.
 11. The treatedgeothermal brine composition of claim 1, further wherein the treatedgeothermal brine has a concentration of rubidium less than about 100mg/kg.
 12. The treated geothermal brine composition of claim 1, furtherwherein the treated geothermal brine has a concentration of rubidiumless than about 50 mg/kg.
 13. The treated geothermal brine compositionof claim 1, wherein the treated geothermal brine is a Salton Seageothermal brine.
 14. A method of using a treated geothermal brinecomposition, the method comprising the steps of supplying thecomposition of claim 1 to a process for mineral extraction.
 15. A methodof using a treated geothermal brine composition, the method comprisingthe step of injecting the composition of claim 1 into a geothermalreservoir.
 16. A treated geothermal brine composition, the compositioncomprising a treated geothermal brine having a concentration of silicaranging from about 0 mg/kg to about 15 mg/kg, a concentration of ironranging from about 0 mg/kg to about 10 mg/kg, and a concentration ofrubidium ranging from about 30 mg/kg to about 200 mg/kg, and comprisingrecoverable amounts of one or more metals selected from the groupconsisting of lithium and cesium or mixtures thereof.
 17. The treatedgeothermal brine composition of claim 16, wherein the treated geothermalbrine is a Salton Sea geothermal brine.
 18. A method of using a treatedgeothermal brine composition, the method comprising the step ofsupplying the composition of claim 16 to a process for mineralextraction.
 19. A method of using a treated geothermal brinecomposition, the method comprising the step of injecting the compositionof claim 16 into a geothermal reservoir.
 20. The treated geothermalbrine composition of claim 16, wherein the treated geothermal brine hasa concentration of potassium of less than about 4000 mg/kg.